Myanmar authorities have cancelled the United Nations’ planned visit to the restive Rakhine state, which has seen a mass exodus of Rohingya Muslims, BBC reported on Thursday.

A United Nations spokesperson in Yangon was quoted as saying that Myanmar gave no reason for cancelling the visit. This would have been the first time representatives of United Nations’ agencies visited the region since violence broke out in Rakhine.

UN Secretary-General António Guterres asked Security Council members to consider taking “swift action” to prevent further instability in the region. “The situation has spiralled into the world’s fastest developing refugee emergency and a humanitarian and human rights nightmare,” Guterres said on Thursday.

Chiefs of UN agencies were expected to participate in the trip. UN Spokesperson Stephane Dujarric had said on Wednesday that he hoped the trip would be “a first step towards much freer and wider access to the area”.

The UN has been demanding access to Rakhine since its organisations were forced to pull out of the state when Myanmar’s military attacked Rohingya militants in August. More than 4.2 lakh Rohingya Muslims have fled to Bangladesh since then.

On September 26, the Human Rights Watch accused the Army of forced deportation, murder, rape and persecution of Rohingya Muslims in the region and said this has led to “countless deaths and mass displacement”. The non-profit had also urged the UN Security Council to ask Myanmar to allow entry to a UN fact-finding mission to investigate the rights abuses.