UN Secretary-General Antonio Guterres has said that ethnic cleansing is taking place in Burma, leading to a "catastrophic" humanitarian situation for the Rohingya Muslim minority with nearly 380,000 people forced to flee to Bangladesh.

The UN Security Council also condemned the violence, with Britain's UN Ambassador Matthew Rycroft calling the statement - the first the UN's most powerful body has made in nine years on the situation Burma - “an important first step.”

The secretary-general has been outspoken about calling for an end to the violence in Burma's Rakhine state, and sent the Security Council an official letter raising his concerns about a crisis — the first time a UN chief has done so since 1989.

Human Rights Watch and Amnesty International had accused the Security Council on Tuesday of ignoring large-scale “ethnic cleansing” of the Rohingyas and demanded that it hold an open meeting and urge an end to the violence.

“It's a first step, but the council needs to escalate this to the level that a crisis that bears the hallmarks of ethnic cleansing deserves,” Human Rights Watch's UN Director Louis Charbonneau said after the council statement. “We haven't seen that yet.”

Mr Guterres at a wide-ranging press conference called Burma one of two world issues “at the top of global concerns,” along with North Korea.

“Grievances that have been left to fester for decades have now escalated beyond Myanmar's [Burma's] borders, destabilising the region,” the secretary-general warned. “The humanitarian situation is catastrophic.”

Last week there were 125,000 Rohingya refugees who had fled to Bangladesh and “the number has now tripled to nearly 380,000,” he said.

Rohingya refugees – in pictures Show all 15 1 /15 Rohingya refugees – in pictures Rohingya refugees – in pictures A young girl and a baby wade through mud after arriving in Whaikhyang, Bangladesh from Burma on 10 September Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya refugees walk through a camp in Whaikhyang, Bangladesh after arriving from Burma Dan Kitwood/Getty Images Rohingya refugees – in pictures A young Rohingya refugee gathers firewood after arriving in Whaikhyang, Bangladesh from Burma Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya refugees wait for sacks of rice to be distributed in Whaikhyang, Bangladesh Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya Muslim refugees arrive on a boat in Whaikhyang, Bangladesh after crossing from Burma on 8 September Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya Muslim refugees react after being re-united with each other after arriving in Whaikhyang, Bangladesh on a boat from Burma Getty Rohingya refugees – in pictures Rohingya Muslim refugees walk along the remains of a road after arriving in Whaikhyang, Bangladesh on a boat from Burma Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya Muslim refugees wade through water after arriving in Whaikhyang, Bangladesh by boat from Burma Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya Muslim refugees wade through water after arriving in Whaikhyang, Bangladesh by boat from Myanmar Dan Kitwood/Getty Images Rohingya refugees – in pictures Rohingya Muslim refugees stand in the rain after arriving in Whaikhyang, Bangladesh by boat from Burma Dan Kitwood/Getty Images Rohingya refugees – in pictures Indian children hold placards and shout slogans during a protest against the alleged persecution of the Rohingya Muslims in Burma EPA/Raminder Pal Singh Rohingya refugees – in pictures Supporters of the Difa-e-Pakistan Council (DPC), an Islamic organisation, listen to their leaders' speeches against Burma's persecution of Rohingya Muslims, during a demonstration in Karachi Reuters/Akhtar Soomro Rohingya refugees – in pictures Hundreds of Iranians take part in a protest against violence in Myanmar after weekly Friday prayers, in Tehran EPA/Abedin Taherkenareh Rohingya refugees – in pictures Indonesian Muslim activists hold placards and shout slogans during a protest against the alleged persecution of the Rohingya minority in Magelang, Central Java, Indonesia EPA/Ali Lutfi Rohingya refugees – in pictures Members of an Islamic organisation shout slogans against the Burma government during a protest in Dhaka, Bangladesh EPA

Mr Guterres was asked whether he agreed with UN human rights chief Zeid Ra'ad al-Hussein that what's happening in Rakhine State is ethnic cleansing. He answered with a question: “When one-third of the Rohingya population had to flee the country, can you find a better word to describe it?”

Rohingya have faced decades of discrimination and persecution by the majority Buddhist population in Burma, where they are denied citizenship despite centuries-old roots in the country.

The current crisis erupted on Aug. 25, when an insurgent Rohingya group attacked police outposts in Burma's Rakhine state, killing a dozen security personnel.

That prompted Burma's military to launch “clearance operations” against the rebels, setting off a wave of violence that has left hundreds dead, thousands of homes burned, and tens of thousands fleeing to Bangladesh.

Mr Guterres reiterated his condemnations of the attacks by the insurgent Arakan Rohingya Salvation Army but said reported attacks by security forces against civilians “are completely unacceptable.”

Rohingya Muslims flee violence in Burma

The secretary-general called on Burma's authorities “to suspend military action, end the violence, uphold the rule of law, and recognise the right of return of all those who had to leave the country.” He also reiterated his call for the government to grant the Rohingyas nationality or at least legal status so they can get jobs, education and health care. Mr Guterres added that he had spoken several times with Burma's national leader, Aung San Suu Kyi.

Ms Suu Kyi has cancelled a trip to the UN General Assembly in New York next week to deal with the crisis. Mr Rycroft said two high-level meetings on Burma were due to be held during the gathering of world leaders at the United Nations.

British Foreign Secretary Boris Johnson will co-host a ministerial-level meeting on Burma, while Turkey is also hosting a meeting organised by the Organisation of Islamic Cooperation.

The UN Security Council statement acknowledged the 25 August attacks on Burma's security forces but it “condemned the subsequent violence”.

Council members in the statement “expressed concern about reports of excessive violence during the security operations and called for immediate steps to end the violence in Rakhine, de-escalate the situation, re-establish law and order, ensure the protection of civilians, restore normal socio-economic conditions, and resolve the refugee problem.”

The Security Council also urged the government to implement the recommendations of a commission led by former UN secretary-general Kofi Annan calling for economic development and social justice to counter deadly violence between Buddhists and Muslims in Rakhine state.

A Security Council diplomat, speaking on condition of anonymity because the consultations were closed, said even though the US, UK, Sweden and others wanted a tougher statement, many council members said it was “a considerable achievement” that all 15 countries including China agreed to send a clear message to Burma's government and military.