“We are frustrated that she has not taken any initiative to ensure full and equal citizenship rights of the Rohingyas,” the group wrote.

In recent weeks, more than 27,000 people belonging to the persecuted Muslim minority – a group loathed by many of Myanmar’s Buddhist majority – have fled a military operation in Rakhine state launched in response to attacks on border posts by armed groups in October in which nine officers were killed.

Rohingya survivors say they suffered rape, murder and arson at the hands of soldiers – accounts that have raised global alarm and galvanised protests around Southeast Asia.

The signatories to the letter said even if a group of Rohingyas was behind the October 9 attacks, the army’s response had been “grossly disproportionate”.

“It would be one thing to round up suspects, interrogate them and put them on trial,” the letter said.

“It is quite another to unleash helicopter gunships on thousands of ordinary civilians and to rape women and throw babies into a fire.”

Myanmar’s government has denied accusations that excessive military force was used following the October attacks.

Bangladesh’s government has been under pressure to open its border to the fleeing refugees, but it has reinforced its border posts and deployed coastguard ships to prevent fresh arrivals.

“The Rohingyas are among the world’s most persecuted minorities, who for decades have been subjected to a campaign of marginalisation and dehumanisation,” said the authors – among them peace prize winners Desmond Tutu, Shirin Ebadi, Malala Yousafzai, Muhammad Yunus and Jose Ramos-Horta. Others who signed include former prime minister of Italy Romano Prodi and British businessman Richard Branson.

They asked the 15-member Security Council to add the “crisis” to its agenda “as a matter of urgency, and to call upon the secretary general to visit Myanmar in the coming weeks” – either current UN chief Ban Ki-moon, or his successor Antonio Guterres, who will take over the post next month.

“If we fail to take action, people may starve to death if they are not killed with bullets, and we may end up being the passive observers of crimes against humanity which will lead us once again to wring our hands belatedly and say ‘never again’ all over again,” the letter said.

The letter was initiated by Ramos-Horta, according to a spokeswoman for the former East Timor president, and Yunus, who helped revolutionise finance for the poorest in Bangladesh. It also called for the Myanmar government to lift all restrictions on humanitarian aid to Rakhine State.

Myanmar’s UN mission was closed Thursday and an email message seeking a response was not immediately returned.

The Rohingya have languished under years of dire poverty and discrimination from a government that denies them citizenship. The UN and other rights groups have repeatedly called on Myanmar to grant them full rights. The previous military government launched a scheme it said would lead to minorities such as Rohingya becoming citizens, but it was scrapped after protests by nationalist Buddhists – including members of Suu Kyi’s pro-democracy movement.

Additional reporting by Associated Press and Reuters