Dhaka The United Nations (UN) will need $200 million (Dh734 million) over the next six months to face the “catastrophic” influx of more than 420,000 Rohingya refugees to Bangladesh, a top UN official said on Friday.

The Rohingya Muslims, escaping ethnic unrest in Myanmar, have overwhelmed Bangladesh’s Cox’s Bazar in under a month.

The UN made an emergency appeal for $78 million on September 9, but UN resident coordinator in Bangladesh, Robert Watkins, said much more would be needed as the exodus grows.

“Our best estimate at this point is $200 million. We are putting together a plan right now that will be ready in about four or five days,” Watkins said.

He said aid workers were already struggling to get food, medicine and drinking water to the refugees, many of whom were limited to one meal a day.

“The fact that there are 430,000 refugees here is in fact a catastrophic event. There is no question about that. We are coping the best we can,” Watkins said.

“We are working very hard with the government to get out assistance to all the people, to make sure that everyone is covered with shelter, getting food and getting access to health care and pure water and sanitation. This is our priority right now.”

He described the government allocation of new land for a massive new refugee camp as a “big breakthrough”.

The 809 hectares of land between two existing camps is already being developed.

“People have been supplied with building materials so they can build their own shelters in the short term. In the medium term they can build something more resilient.”

He also offered UN help in government attempts to register refugees.

“The government has started doing that. We have been offering the government to assist with our biometric registration technology and staff and that is still being negotiated with the government.”

The registration could play an important role in any future accord to send Rohingya back to Myanmar, where the Buddhist-dominated army has been accused of killing Rohingya and burning their villages.

A huge relief operation has started with truck convoys carrying aid to some of the remotest border areas.

Some 100 tonnes of food, tents, sleeping mats and blankets sent by Saudi Arabia have started arriving in Cox’s Bazar. The United States has also pledged $32 million to help Bangladesh cope with the influx.

The International Organisation for Migration said the Saudi aid would be distributed “to some of the thousands of people who have arrived from Myanmar with nothing and are now camped out and living rough on the side of the road or in muddy fields.”

“We urgently need more supplies like food, water, medicine and shelter. We can and we must do more,” Save the Children International chief executive Helle Thorning-Schmidt said at UN in New York.

The top US diplomat for Southeast Asia said America remains deeply troubled by the ongoing crisis and allegations of human rights abuses in Myanmar’s Rakhine state, where hundreds of thousands of Rohingya have fled government security operations in recent weeks.

US Deputy Assistant Secretary of State for Southeast Asia Patrick Murphy, speaking on Friday in a conference call from Bangkok, said while the US condemns August attacks by Muslim Rohingya militants, the response from Myanmar’s security forces has been “disproportionate”. He called on security forces to end the violence in Rakhine, stop vigilantism there, protect civilians and facilitate humanitarian assistance in the area.

Murphy also called on the security forces to work with the civilian government to implement the recommendations of a committee headed by former UN Secretary-General Kofi Annan.

More than 420,000 Rohingya refugees have fled from Myanmar to Bangladesh in less than a month, with most ending up in camps in the Bangladeshi district of Cox’s Bazar, which already had hundreds of thousands of Rohingya refugees who had fled prior rounds of violence in Myanmar.

The latest violence began when a Rohingya insurgent group launched deadly attacks on security posts August 25, prompting Myanmar’s military to launch “clearance operations” to root out the rebels. Those fleeing have described indiscriminate attacks by security forces and Buddhist mobs. The government has blamed the Rohingya, saying they set fire to their own homes, but the UN and others accuse it of ethnic cleansing.

Rohingya have faced persecution and discrimination in majority-Buddhist Myanmar for decades and are denied citizenship, even though many families have lived there for generations. The government says there is no such ethnicity as Rohingya and that they are Bengalis who illegally migrated to Myanmar from Bangladesh.

Murphy said the US ultimately wants Rohingya to be able to return to their homes in northern Rakhine state.

He said the US welcomed Myanmar leader Aung San Suu Kyi’s decision to speak publicly about the problem this week. He also said the US realises that Suu Kyi has limited control over the security forces due to the nation’s “flawed constitution”, which allows the military to remain politically powerful and guarantees it control of key ministries including those related to security and defence.

There are many stakeholders responsible for solving the crisis in Rakhine including Suu Kyi’s civilian government, the military, local officials and the people on the ground, Murphy said.

He said the US has warned Myanmar about potential repercussions it faces if it doesn’t address the crisis including greater instability in Rakhine, threats to the stability of its borders, the risk of attracting international terrorists, scaring off investment and ultimately, stunting its transition to democracy.

Murphy called on everyone in Myanmar to work to “lower the rhetoric and lower the tensions”, including on social media, which he said has been used to spread hate speech and misinformation campaigns. He said everyone in Myanmar, which was ruled by a military junta until 2012, had suffered at one time or another.

“We appeal to all people to remember their own circumstances and show compassion,” he said. “We hope they can come to the conclusion that no human being should suffer in this manner.”

He acknowledged that the US and others don’t have access to all the facts on the ground in Rakhine and said Washington is pushing Myanmar to end its ban on media access to the region. Still it was clear what the impact of events in Rakhine had been, he said.

“The proportions of such human movements are staggering,” Murphy said.