An attack on an aid shipment in Myanmar's violence-wracked Rakhine state and a deadly Red Cross truck crash in Bangladesh on Thursday hampered desperately needed relief efforts for Rohingya Muslims fleeing persecution.

Communal tensions remain high across Rakhine where raids by Rohingya militants at the end of last month sparked a massive army crackdown, driving more than 420,000 people into Bangladesh in what the United Nations (UN) has called a campaign of “ethnic cleansing”.

Tens of thousands of Muslim Rohingyas, who are widely reviled in the Buddhist-majority Myanmar, are feared to be trapped in hard-hit areas of Rakhine state, while humanitarian agencies in neighbouring Bangladesh are strained by the massive refugee influx.

The crisis has prompted a global chorus of condemnation against Myanmar's government for failing to blame the all-powerful military for the renewed violence, which French President Emmanuel Macron called a “genocide”.

The UN has called for unhindered access to Rakhine state, which has been mostly closed to media and humanitarian groups.

An International Committee of the Red Cross (ICRC) ship carrying 50 tonnes of aid was halted by a 300-strong Buddhist mob in the state capital Sittwe on Wednesday night.

The group forced the ICRC to unload the aid from the boat and prevented the vessel from leaving, state-backed Global New Light of Myanmar newspaper reported Thursday, quoting Myanmar's Information Committee.

The crowd hurled “stones and Molotov (cocktails)” at riot police on the scene, injuring several officers before order was restored.

The ICRC confirmed the incident and said its staff were not injured, vowing to continue to try to deliver aid.

“We will carry on, nothing has been put on hold,” Graziella Leite Piccoli, ICRC spokeswoman for Asia, told AFP.

News of the clashes emerged as a truck hired by the Red Cross and ICRC crashed in Bangladesh, killing nine people and injuring 10 others.

“It was carrying the food to Rohingya refugees on the border, including those stranded in the no-man's land,” Yasir Arafat, deputy police chief of Bandarban border district, told AFP.

Aid airlift

Hundreds of thousands of Rohingya refugees have streamed into Bangladesh since the end of August, cramming into ill-equipped camps and makeshift shelters near the border town of Cox's Bazar.

Aid groups say they are overwhelmed by the massive influx, and though the Bangladeshi government is building a new camp in the area it will be some time before it is fully equipped.

Saudi Arabia is airlifting 100 tonnes of donated tents, sleeping mats, blankets and food to refugees in Bangladesh, said the International Organization for Migration (IOM), which is chartering the flight.

“Many of these families are still living in the open without adequate shelter, food or clean water,” Mohammed Abdiker, IOM Director of Operations and Emergencies, said in a statement.

Myanmar's de facto leader Aung San Suu Kyi has come under fire for downplaying the violence and failing to condemn the military crackdown against the Rohingya, a marginalised group the government considers illegal “Bengali” immigrants.

Amid urgent calls from the UN for humanitarian access this week, Myanmar insisted the crisis was easing.

“I am happy to inform you that the situation has improved,” second vice president Henry Van Thio told the UN General Assembly on Wednesday.

He said there have been no clashes since September 5 in Rakhine, where the military has been accused of burning scores of villages to the ground sending terrified Rohingya villagers fleeing.

“Humanitarian assistance is our first priority. We are committed to ensuring that aid is received by all those in need, without discrimination,” he said.

There were more than one million Rohingyas in Rakhine state before the current crisis, though nearly half have fled since the deadly attacks on military posts by militants from The Arakan Rohingya Salvation Army (ARSA) on August 25.

The Rohingya have long been sidelined in Myanmar, where they are considered illegal immigrants and face severe restrictions.

Myanmar's army chief on Thursday said the Rohingya population “exploded” under British rule, blaming the former colonists for the current crisis.

“The Bengali population exploded and the aliens tried to seize the land of local [ethnicities],” Min Aung Hlaing said in comments posted on Facebook, using a term Rohingya consider derogatory.

Britain said this week it had suspended its educational training courses for the Myanmar military due to the violence, amid a mounting diplomatic spat between the countries.