Stuck between the brutal crackdown by the Myanmar army and a closed border with Bangladesh, the ethnic Rohingya Muslims' chance of survival is slim. Since Friday, "thousands of Muslims were killed" according to the European Rohingya Council as security forces launched operations against what they called a series of attacks by Rohingya "insurgents" in the north of the country's Rakhine State, home to the ethnic group in Buddhist-majority Myanmar.

Bangladesh, home to more than 400,000 Rohingya Muslims who fled the systematic persecution in Myanmar, turned down appeals to open the borders.

Bangladeshi border guard officials told Reuters they had sent back about 550 Rohingya since Monday, via the Naf river that separates the two countries. United Nations Secretary-General Antonio Guterres called on Dhaka to let Rohingyas in. A senior border guard official speaking to AFP said around 6,000 Myanmar nationals have gathered on the border and were trying to enter the country. Some 3,000 people managed to cross into the country according to figures by a U.N. refugee agency.

The Bangladeshi official said the situation was "still volatile," noting heavy gunfire by automatic weapons and smoke over burnt villages across the border. Officials expect thousands more to arrive on the border from hills and forests they have been hiding near the border. An 11-year-old Rohingya girl named Marium was separated from her parents amid the turmoil. Stranded on the border, the crying girl told AFP she was in the toilet when the guards drove her parents away. "Where shall I find them now?" she wailed. Mohammad Ismail had taken shelter from the rain under a plastic sheet erected by border guards just inside Bangladeshi territory, but the shelter has since been torn down.

"The border guards let us take shelter here, but I don't know now what I will do with my son," he told AFP, gesturing to the shivering boy. Speaking to Anadolu Agency (AA), Anita Schug, spokeswoman for the European Rohingya Council, said 2,000 to 3,000 Muslims died in Rakhine state between Friday and Monday. She said thousands of others were injured in "a slow-burning genocide." She said almost a thousand Muslims were killed on Sunday in Saugpara village, Rathedaung alone. The region has seen simmering tension between its Buddhist and Muslim populations since communal violence broke out in 2012.

A security clampdown launched in October last year in Maungdaw, where Rohingya form the majority, led to a U.N. report on human rights violations by security forces that indicated crimes against humanity.

The U.N. documented mass gang rape, killings, including that of babies and children, brutal beatings and disappearances.

Reuters reported that an estimated 5,000 Rohingya have been able to cross into Bangladesh over the past few days, most slipping in at night over the land border near the Bangladeshi village of Gumdhum. Many are sick and at least six have died after crossing in, an aid worker said, adding that fear of being caught and sent back meant some refused to seek help. "What we're seeing is that many Rohingya people are sick," said the worker with an international agency in Bangladesh who declined to be identified or have his agency identified. "This is because they got stuck on the border before they could enter. It's mostly women and children. "We're making all out efforts but a rapid response is needed," the aid worker said. "Some are refraining from getting treatment to avoid arrest." Rohingya Muslims, who trace their roots to Myanmar centuries ago, are denied citizenship by Myanmar that defines them as illegal immigrants. They are often subject to violence by Buddhist extremists.