Saudi Arabia's King Salman on Sunday slammed Iran's “blatant interference” in regional affairs as Arab leaders met in the kingdom for an annual gathering.

Opening the 29th Arab League summit, the king also criticised the US decision to transfer its embassy in Israel to Jerusalem and described “terrorism” as the biggest challenge facing Arab countries.

Seventeen leaders from across the Arab world — minus Syrian President Bashar al-Assad — gathered in the eastern Saudi city of Dhahran for the summit, which this year comes as world powers face off over Syria and tensions rise between Riyadh and Tehran.

The meeting opened only 24 hours after a barrage of strikes launched by the United States, Britain and France hit targets they said were linked to chemical weapons development in Syria, which was suspended from the league seven years ago.

But King Salman avoided any mention of Syria in his address, as a seat marked “Syrian Arab Republic” sat empty in the hall.

Instead, the king focused on rivalries with long-time foe Iran — only 160 kilometres (100 miles) across the Gulf from Dharan.

“We renew our strong condemnation of Iran's terrorist acts in the Arab region and reject its blatant interference in the affairs of Arab countries,” the king said.

Donation for East Jerusalem

Saudi Arabia's King Salman on Sunday announced a $150 million donation for the maintenance of Islamic heritage in East Jerusalem.

“Saudi Arabia announces a $150 million grant to support the administration of Jerusalem's Islamic property,” the monarch said at the opening of the Arab League summit in the kingdom's eastern city of Dhahran.

“I name this summit in Dhahran the Jerusalem Summit so that the entire world knows Palestine and its people remain at the heart of Arab concerns,” he said.

The funding announcement came as the king reiterated criticism of President Donald Trump's decision to recognise Jerusalem as Israel's capital and shift the US embassy from Tel Aviv to the holy city.

The move has sparked deep anger among the Palestinians — who see East Jerusalem as the capital of their future state — and across the Arab world.

“We reiterate our rejection of the US decision on Jerusalem,” Salman said. “East Jerusalem is an integral part of the Palestinian territories.”

Arab ministers at a preliminary meeting in Riyadh on Thursday focused heavily on blocking the move, unanimously condemning Trump's decision.

Israel occupied mainly Palestinian east Jerusalem in the 1967 Six-Day War and later annexed it in a move never recognised by the international community.

Islamic holy sites in the city — including the revered Al-Aqsa mosque — are administered by a Jordanian-run trust known as the Waqf.

King Salman also announced a $50 million donation to UNRWA, the UN agency for Palestinian refugees.

The organisation, which provides aid to more than three million people, faces serious financial difficulties after the US announced it was cutting its funding of the body.

Tough, unified stance against Iran

Saudi Arabia is pushing for a tough, unified stance against its regional arch-rival Iran. The two regional titans back opposing sides in a range of hotspots across the Middle East, including Lebanon and Syria and in Saudi Arabia's southern neighbour Yemen.

Last month the Security Council issued a statement condemning Huthi missile attacks on Saudi, but did not name Iran.

In February, Russia vetoed a Security Council resolution that would have expressed concern over Iran's failure to block supplies of missiles to Yemen's Huthi rebels.

The summit also comes with Saudi Arabia and Qatar locked in a months-long diplomatic standoff, with Riyadh accusing Doha of supporting Islamist extremists and being too close to Iran.

Tensions have eased slightly in recent months but Qatar still only sent its representative to the Arab League for the Dhahran summit.

Among the leaders in attendance was Sudan's Omar al-Bashir, who walked the red carpet and was greeted by King Salman. Bashir is wanted by the International Criminal Court for five counts of crimes against humanity, three counts of genocide and two counts of war crimes.

Summits of the Arab League, established in 1945, rarely result in action.

The last time the bloc made a concrete move was in 2011, when it suspended Syria's membership over the Assad regime's role in the war.

Syria's war, the most complex of the region's conflicts, is the main point of contention pitting Riyadh and its allies, who mainly back Sunni rebels, against regime backer Iran and its Lebanese ally Hezbollah.

Gulf Arab states have made massive donations to Syria but have not officially offered asylum to Syrians.