Relief agencies struggling to reach hundreds of thousands of Rohingya Muslims displaced by strife in northwestern Myanmar are facing rising hostility from ethnic Rakhine Buddhists who accuse the United Nations and foreign aid groups of only helping Muslims.

So far, the Myanmar government has only granted Red Cross organisations access to the area. The United Nations suspended its activities and evacuated non-critical staff after the government suggested it had supported Rohingya insurgents.

Already battling against bad weather, tough terrain and obstructive bureaucracy, the Red Cross also ran into an angry mob, who believe the foreign aid agencies have ignored the suffering of Rakhine Buddhists in Myanmar's poorest state.

On Wednesday a mob in Sittwe, the capital of Rakhine State, tried to block a boat carrying International Committee of the Red Cross (ICRC) aid to the north, where attacks by Rohingya militants on Aug. 25 prompted Myanmar's generals to order a sweeping counter-insurgency offensive.

The mob was armed with sticks, knives and petrol bombs, and only dispersed after police fired rubber bullets.

Four days earlier a Myanmar Red Cross truck was stopped and searched by Rakhine residents in Sittwe.

"With heightened tensions in Rakhine State, humanitarian staff and private contractors are facing serious challenges in implementing life-saving activities," said Pierre Peron, spokesman for the U.N. Office for the Coordination of Humanitarian Affairs in Myanmar.

In the past month, 420,000 Rohingya have fled into neighbouring Bangladesh to avoid what the U.N. human rights chief has called ethnic cleansing.

Foreign aid groups are now scaling up to help Bangladesh cope with a humanitarian disaster of biblical proportions.

Back in Myanmar, a separate crisis is unfolding on multiple fronts, many of them much harder to reach.

"Many ongoing humanitarian activities that existed before August 25th have still not resumed," said Peron. "For the sake of vulnerable people in all communities in Rakhine State, urgent measures must be taken to allow vital humanitarian activities to resume."

In northern Rakhine, tens of thousands of people, most of them Rohingya, are displaced but haven't crossed into Bangladesh.

Closer to Sittwe, 140,000 Rohingya displaced by previous religious unrest are confined to squalid camps. They depend on foreign aid that has been severely restricted since Aug. 25.

About 6,000 Buddhists have also fled to Sittwe, where they are cared for at monasteries by the government and Rakhine volunteers.

BROKEN TRUST

Ethnic Rakhine have long complained that foreign aid agencies have given generously to Muslims while ignoring other equally needy people.

"All people in Rakhine are suffering, but only Muslims get help," said Htun Aung Kyaw, chief of the Arakan National Party (ANP).

Rakhine residents of Sittwe interviewed by Reuters said they believed that U.N. estimates of refugee numbers were exaggerated, and that Rohingya camps near the city faced no shortages.

"They have more than enough," said Kyaw Sein of Rakhine Alin Dagar, a Rakhine advocacy group in Sittwe.

Kyaw Sein said she hadn't visited the camps, but said in the past she had seen Muslims selling oil, rice and other aid in local markets.

She said relations between the foreign aid groups and the Rakhine people had been poisoned by years of neglect and favouritism.

"It's difficult to say what they can do to win back our trust," she said.

"BIGGER ATTACKS"

Further eroding that trust are rumors that aid deliveries could be used to smuggle weapons to the Arakan Rohingya Salvation Army (ARSA), the militant group behind the attacks on security forces last month and in October 2016.

"The Rakhine have no weapons to protect themselves with," said the ANP's Htun Aung Kyaw. "That's why they're so terrified."

Such fears have been stoked by social media and by the discovery of World Food Program-branded biscuits at a suspected militant camp on July 30.

They have also prompted the authorities to restrict humanitarian access to some Rohingya villages on security grounds, say aid workers.

Htun Aung Kyaw predicted "bigger and bigger attacks", especially if ARSA drew support from groups such as Islamic State.

Those concerns were echoed on Thursday by U.S. Deputy Assistant Secretary of State Patrick Murphy, who warned of "a more significant terrorism problem" if the Rakhine crisis was not properly addressed.

Murphy also criticized the Myanmar security forces for "a response that is disproportionate and failed to protect all local populations."

The United Nations rights body has called it "a textbook example of ethnic cleansing", with reports of hundreds of Muslim villages razed and abuses by soldiers, police and Rakhine vigilantes.

Even so, many people in Myanmar - not just Rakhine - appear to believe the military's explanation: the Rohingya set their own houses alight before fleeing.

Rakhine interviewed by Reuters said the Rohingya did this to win sympathy from aid groups, galvanise opposition in the Muslim world and ensure that nearby Rakhine houses burned down too.

Some aid workers privately scoffed at such views, but they also admitted that their early failure to engage and understand the Rakhine has made their current work more difficult.

Graziella Leite Piccoli, the ICRC's regional spokesperson, said aid workers "should never be targeted", and her colleagues were working to convince local communities that they are there to help everyone.