At least 86 people have been killed in a military crackdown in Rakhine State, launched after attacks on police posts near the border with Bangladesh on Oct. 9.
The government of predominantly Buddhist Myanmar has blamed Muslim Rohingyas supported by foreign militants for the coordinated attacks which killed nine police officers.
More than 30,000 people have fled to Bangladesh, escaping the violence which has renewed international criticism that Aung San Suu Kyi's government has done too little to help the Rohingya, who are denied citizenship in Myanmar.
In an open letter to the Security Council, Tutu and 22 others including fellow Nobel Peace laureates José Ramos-Horta and Muhammad Yunus said a "human tragedy amounting to ethnic cleansing and crimes against humanity is unfolding in Myanmar".
"If we fail to take action, people may starve to death if they are not killed with bullets," the letter said.
The violence had the hallmarks of Rwanda's 1994 genocide as well as ethnic cleansing in Sudan's western Darfur region, Bosnia and Kosovo, it said.
The signatories to the letter said even if a group of Rohingyas was behind the Oct. 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.
The letter was initiated by Ramos-Horta, according to a spokeswoman for the former East Timor president, and Yunus, who helped revolutionize finance for the poorest in Bangladesh.
A spokeswoman for the presidency of the 15-member Security Council, currently held by Spain, confirmed it had received the letter, which also expresses frustration that Suu Kyi, the 1991 Nobel Peace Prize winner, had not ensured citizenship rights to Rohingyas.
The letter also called for the Myanmar government to lift all restrictions on humanitarian aid to Rakhine State.
Officials from Myanmar's mission to the United Nations in New York were not immediately available for comment.
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