At least 18,500 Rohingya have crossed into Bangladesh since fighting erupted in Myanmar's neighbouring Rakhine state six days ago, the International Organization for Migration said Wednesday.

Plumes of smoke billowed from several burning villages in the worst-hit section of the state, according to an AFP reporter on a government-led trip to the area, as the violence showed little sign of abating despite security sweeps by Myanmar's police and troops.

The clashes began on Friday after militants from Myanmar's Rohingya Muslim minority community staged deadly surprise raids on police posts.

At least 110 people, including 11 state officials, have been confirmed dead and thousands of Rohingya have poured across the border to Bangladesh despite Dhaka's attempts to stop them.

"As of last night, 18,500 people have come across," Chris Lom, the IOM's Asia-Pacific spokesman, told AFP, adding an unknown number were still stuck on the Myanmar side of the border.

Lom said exact figures were difficult to obtain because many of those who crossed into Bangladesh might not have registered with local authorities. 

On Tuesday an estimated 6,000 had massed at the "zero line" border with Bangladesh, days after the area came under mortar and machine gun fire by Myanmar security forces.

The Rohingya, the world's largest stateless minority and subject to severe restrictions on their movements, are barred from officially crossing.

Bangladeshi authorities on Wednesday toughened patrols in a bid to prevent more arrivals in a country that already hosts an estimated 400,000 Rohingya.

Rohingya have sneaked across the land border in large number or swum the Naf River which marks part of the frontier. But tragedy befell some of them.

The bodies of two Rohingya women and two children washed up on Bangladeshi soil on Wednesday, an official there told AFP, victims of drowning after their rickety boat capsized.

Among the dead and displaced are also ethnic Rakhine Buddhists and other tribal groups, who say they were targeted by the Rohingya militants.

A boatload of tired-looking displaced people arrived in the Rakhine state capital Sittwe on Wednesday afternoon after being evacuated from Buthiduang township, one of the epicentres of the violence. 

A few hours further west towards Bangladesh, Rohingya villagers said their homes had been set on fire by security forces. 

"Villagers are running away... where do we have to live now?" one told AFP from a village near Maungdaw, speaking on condition of anonymity.

It was not immediately possible to verify his account but Rohingya who have made it into Bangladesh have brought similar testimony with them.

Large fires were visible early Wednesday from the May Yu river that cuts through the area worst hit by unrest, according to the AFP reporter.

- Maximum restraint? -

Outlying villages in Myanmar have witnessed some of the worst violence, raising fears security operations are shielded from scrutiny by the danger and inaccessibility of the area.

Rohingya villagers are stuck between police and troops hunting down the insurgents and militants offering sporadic resistance.

But witnesses among the displaced reaching Bangladesh have told AFP some Rohinyga men are heeding a call to arms by the militants and staying behind to fight in their villages.

The Arakan Rohingya Solidarity Army claims its men launched Friday's surprise attacks on police posts, killing 11 state officials, with knives, homemade explosives and a few guns. 

After years in which the Rohingya largely avoided violence, the group last October carried out deadly attacks on police posts.

That prompted a months-long security crackdown by Myanmar's army which left scores dead and forced 87,000 people to flee to Bangladesh.

The UN believes that military crackdown may have amounted to ethnic cleansing of the Rohingya -- allegations denied by the army.

On Sunday Pope Francis led mounting international calls for the protection of "our Rohingya brothers".

The UN has also urged Myanmar to protect civilians during its operations and called on Bangladesh to allow the displaced into their territory.

A Myanmar government official on Tuesday said security forces would use "maximum restraint" in coming days but insisted on the country's right to defend itself from "terrorists".

Source: AFP