The United Nations has said it fears a greater human rights catastrophe in Myanmar amid reports of thousands of troops massing in the north of the Southeast Asian country which has been in chaos since a February coup.

UN Special Rapporteur on Myanmar Tom Andrews, who was presenting the findings of an annual human rights report on Myanmar to the UN General Assembly on Friday, said he had received information that tens of thousands of troops and heavy weapons were being moved into restive regions in the north and northwest.