CAIRO/RIYADH: A five-day truce in Yemen appeared to be broadly holding on Wednesday, despite reports of air strikes overnight by Saudi-led forces and continued military activity by the country's dominant Houthi group.

Rockets hit border areas in Saudi Arabia from Yemen's rebel-held north, a Saudi defence ministry official said. “At 10:00 am (0700 GMT) on Wednesday, rockets fell on the regions of Najran and Jazan, and (rebel) Houthi militia sniper fire was detected, but there were no casualties,” said the official quoted by the Saudi Press Agency.

Saudi armed forces “practised self-restraint as part of their commitment to the humanitarian truce which was decided by coalition forces,” the official said.

“We are committed to respect this [ceasefire],” coalition spokesman Brigadier General Ahmed al-Assiri had said, but the coalition would continue its “intelligence, reconnaissance and surveillance” in case it had to respond, he added.

“We will be ready to react to any violation of the pause,” Assiri told AFP.

Witnesses in the southwestern city of Abyan said warplanes had hit positions there after the Houthis seized the area following the start late on Tuesday of the ceasefire, which is intended to ward off a humanitarian catastrophe.

Residents of the southern provinces of Shabwa and Lahj, which have witnessed heavy ground clashes between local militiamen and the Houthis, also reported air strikes overnight.

At least 35 civilians were killed by the Saudi-led attacks on the cities of Abs and Zabeed in western Yemen on Tuesday, residents said, before the beginning of the ceasefire.

Seeking to restore exiled President Abd-Rabbu Mansour Hadi, an alliance of Gulf Arab nations has since March 26 been bombing Houthi militia and allied army units that control much of Yemen.

In the bulwark of opposition to the Houthis in the southern city of Aden, the scale of over six weeks of clashes emerged.

Over 600 people had been killed and 3,000 had been wounded, while 22,000 residents had been displaced since the Houthis first pushed into the city on March 25, local watchdog group, the Aden Centre for Monitoring, said on Wednesday.

Residents expressed doubts that the break in fighting, which paused round-the-clock gunfire that had defined Aden life in recent weeks, would last.

“Aden needs a humanitarian truce so badly, given the lack of food, fuel and everything else. But we question the intentions of the Houthis and believe they will take advantage of the truce to take more areas,” resident Hassan al-Jamal said.

Saudi Arabia and its Sunni Muslim allies believe the Houthis are a proxy for Iran in a regional power struggle that has exacerbated sectarian tensions across the Middle East.

Just before the five-day pause took effect at 2000 GMT on Tuesday night, the coalition warned Yemen's Iran-backed rebels it would strike back at any violation.

Pakistan welcomes humanitarian ceasefire

Pakistan welcomed the five-day ceasefire announced by Saudi Arabia for provision of humanitarian assistance to the people of Yemen.

According to a statement issued by the Foreign Office, the Pakistan government has decided to provide one million dollars for humanitarian assistance to the brotherly people of Yemen in view of the close and cordial relations between the peoples of Pakistan and Yemen.

The statement said that the assistance will be provided in coordination with King Salman Centre for Relief and Humanitarian Assistance, established in Riyadh.

Aid and medicine

Saudi state television quoted an official source at the Defence Ministry as saying projectiles had fallen on the Najran and Jizan areas on Wednesday morning and that some sniper fire by the Houthis had been detected. There were no casualties.

“The position adopted by the armed forces was to exercise restraint, abiding by the humanitarian truce approved by the coalition forces,” the television quoted the official as saying.

There was no immediate confirmation of the accusations by Saudi media.

The truce is meant to allow in aid and medicine to Yemen, where the United Nations believes 828 civilians, including 182 children, have been killed since March 26.

There was no word of any new aid arriving by Wednesday afternoon.

The scattered reports of incidents would suggest violence at a far lower level than before the truce formally began.

The Houthi TV channel al-Masira said Saudi ground forces shelled their northern stronghold province of Saada and called the bombings a violation of the ceasefire.

The Saudi state news agency SPA said King Salman, at a royal court ceremony attended by President Hadi and Yemeni Prime Minister Khaled Bahah, authorised the laying of the foundation stone for a humanitarian relief centre.

The Saudi-owned al-Arabiya channel said the monarch had allocated one billion riyals ($265 million) to the Yemen relief work, in addition to a similar amount he had pledged earlier.

Saudi king doubles Yemen aid pledge to $540 million

King Salman doubled Saudi Arabia's Yemen aid commitment to $540 million on the first day of the humanitarian ceasefire.

“We announce that we are setting aside one billion riyals ($266m) for aid and humanitarian operations ... In addition to more than one billion riyals ($274m) we had already pledged,” the official Saudi Press Agency quoted the king as saying.

On April 18, the kingdom announced it would fund the entire $274m sought by the United Nations in an appeal for emergency assistance to help victims of the war in Yemen.

The UN said the money would “meet the life-saving and protection needs of 7.5m people affected” by a deepening humanitarian crisis in Yemen.

“Projects and partners have been identified for implementation of the grant but money has not been disbursed yet, so it is still a pledge,” Jens Laerke, spokesman for the UN Office for the Coordination of Humanitarian Affairs, said on Tuesday.

UN agencies have prepared for a massive aid operation during the five-day humanitarian pause.

Distribution began on Wednesday of fuel whose scarcity had halted aid deliveries, officials said.

Salman made the pledge while symbolically laying the foundation stone of a facility in Riyadh which he said “will be a leading international centre to help relieve communities that suffer from disasters”.

It will work in coordination with “internationally approved relief organisations” and will pay particular attention to the humanitarian needs of Yemen, he said.

Asked about a Saudi bid to coordinate aid, Laerke said the UN's emergency relief coordinator supervises international relief “and we're very happy that the Saudis and any other parties who want to provide aid coordinate through that mechanism."

Iran warns US against stopping Yemen-bound aid ship

A senior Iranian commander warned the United States that a “fire might start” over an aid ship bound for Yemen on Wednesday after the Pentagon urged it to change course.

Brigadier General Masoud Jazayeri said it was Iran's right to deliver relief supplies to Yemen as the humanitarian ceasefire takes hold, and rejected Washington's request that aid be taken instead to a United Nations hub to allay worries the cargo might be military.

“I should say frankly that Iran's restraint has a limit,” Jazayeri, a deputy chief of staff, told Iran's Arab-language Al-Alam television late on Tuesday. “Saudi Arabia and its novice rulers and the Americans and others should know if they continue to create obstacles on Iran's aid delivery a fire might start that would definitely be out of their control ... My strict recommendation is that they let Iran and other countries deliver their humanitarian aid to Yemen."

The Pentagon said Tuesday it was tracking the aid ship, named Iran Shahed, after a naval commander told state media that Tehran would send warships to escort it to Yemen.

Spokesman Colonel Steven Warren called for the ship to divert to Djibouti, where the UN has set up an aid hub across the narrow strait that separates Yemen from the Horn of Africa, to prove that its cargo was humanitarian.

“The Iranians have stated that this is humanitarian aid,” Warren told reporters in Washington.

“If that is the case, then we certainly encourage the Iranians to deliver that humanitarian aid to the United Nations humanitarian aid distribution hub, which has been established in Djibouti."

The Iranian Red Crescent has said the vessel is carrying 2,500 tonnes of humanitarian aid and has insisted that “no one has the right to inspect” it.

Foreign ministry spokesman Marzieh Afkham reiterated those remarks Wednesday, noting Iran hopes “that with the coordination of the UN aid office, supplies will reach Yemenis as soon as possible."

But she added: “We will not permit countries involved in the Yemen war to inspect our ships carrying our humanitarian aid."

Iranian officials have said the ship is bound for the rebel-held port of Hodeida on Yemen's Red Sea coast and has 60 people on board.

They include seven anti-war activists from France, Germany and the United States, as well as 15 medical staff, 13 media representatives and 25 crew, according to Iranian media.

The standoff over the vessel raises the prospect of a potential confrontation between Washington and Tehran in the vital sea lane which links the Gulf and the Indian Ocean with the Mediterranean though the Suez Canal.

(With additional input by Irfan Haider in Islamabad)