Myanmar’s government said it had evacuated at least 4,000 non-Muslim villagers amid ongoing clashes in northwestern Rakhine state, as thousands more Rohingya Muslims sought to flee across the border to Bangladesh on Sunday.

The death toll from the violence that erupted on Friday with coordinated attacks by Rohingya insurgents has climbed to 104, the vast majority militants, plus 12 members of security forces and several civilians, according to a Reuters tally based on official releases.

The government said it was investigating whether members of international aid groups had been involved in an alleged siege by the insurgents of a village in Rakhine.

The United Nations had pulled out non-essential staff from the area, said a spokesman, while Pope Francis expressed his solidarity with the Muslim minority in his weekly address in Rome.

Bracing for more violence, thousands of Rohingya, mostly women and children, attempted to forge the Naf river separating Myanmar and Bangladesh and the land border. Reuters reporters at the border heard gunfire from the Myanmar side, which triggered a rush of Rohingya towards the no man’s land between the countries.

The violence marks a dramatic escalation of a conflict that has simmered in the region since last October, when a similar but much smaller Rohingya attack prompted a brutal military operation dogged by allegations of serious human rights abuses.

The treatment of approximately 1.1 million Muslim Rohingya in mainly Buddhist Myanmar has emerged as the biggest challenge for national leader Aung San Suu Kyi.

Meanwhile, Bangladesh has detained and forcibly returned 90 Rohingya migrants to Myanmar, police said Sunday, just hours after Myanmarese troops on the other side of the border had opened fire on people fleeing the country.

Police intercepted a group of 70 Rohingya late Saturday after they crossed the “zero line” border zone, where Myanmar soldiers earlier fired mortars and machine guns at villagers making the dangerous dash from the northern state of Rakhine into Bangladesh.