Speaking at a Security Council session convened on Tuesday for the one-year anniversary of the start of the exodus of 720,000 Rohingyas to Bangladesh, Guterres also condemned the attacks by extremists against the security forces.

Describing the Rohingya refugee situation as one of the worst humanitarian and human rights crises of the past year, Secretary-General Antonio Guterres has called for international action to ensure Myanmar is held to account for the crimes of its security forces.

Speaking at a Security Council session convened on Tuesday for the one-year anniversary of the start of the exodus of 720,000 Rohingyas to Bangladesh, Guterres also condemned the attacks by extremists against the security forces.

However, he added that nothing can ever justify the disproportionate use of force against civilians and the horrendous violation of human rights violations by the security forces.

Urging united action by the divided Security Council, Guterres cited a report issued on Monday by a UN Human Rights Council (UNHRC) fact-finding team and said the human rights abuses amounted to "the gravest crimes under international law".

He thanked the Bangladesh government for its generosity in hosting the refugees and said more needs to be done by the world community as only 33 per cent of the $951 million UN appeal for assistance has been met and the the monsoon season looms.

The current crisis began in August 2017 with attacks on Myanmar security posts by the Arakan Rohingya Salvation Army (ARSA), which is led by Karachi-born Ata Ullah.

The Myanmar armed forces and vigilantes retaliated brutally against the Rohingyas starting an exodus that began on August 25.

Tariq Mahmood Ahmad, the British Minister of State for the UN, who presided over the Security Council session, said that it should be prepared to use all the tools it has to ensure justice for the Rohingyas.

The strongly-worded report by the UNHRC team headed by former Indonesian attorney-general Marzuki Darusman said that allegations of genocide against Myanmar officials should be referred to the International Criminal Court (ICC) or to a special tribunal.

The Netherlands and Sweden backed the suggestion and asked the Security Council to refer the matter to the ICC.

But Russia and China countered saying that the situation required a non-confrontational approach and only a bilateral diplomatic solution involving Myanmar and Bangladesh would work.

Myanmar’s Permanent Representative Hau Do Suan said that his country did not accept the findings of the UNHRC team as it was biased.

However, he added that Myanmar does not condone human rights abuses and would take action against anyone guilty if there was evidence of their conduct.

He alleged that the ARSA had set up terrorist bases in some areas along the border with Bangladesh.

Bangladesh Permanent Representative Masud Bin Momen said that in the light of the UNHRC team’s report, it was imperative that the Security Council should act decisively.

He said that the Rohingyas could not return to their homes in Rakhine state unless they were assured of their safety.

For this, the Myanmar government should take several steps like curbing hate speech, allowing free access to UN agencies for relief operations and dismantling internal camps for Rohingyas and giving them freedom of movement.

Australian-born actor Cate Blanchett, who is a Goodwill Ambassador for the UN High Commissioner for Refugees, spoke at the Security Council session about her encounters with Rohingya refugees who told her harrowing tales of their experiences in Myanmar.

She said that as a mother she was moved by the plight of the children she met as she saw her children reflected in them.