By Nellie Peyton

DAKAR (Reuters) – An estimated 50,000 people have fled Boko Haram attacks in southeast Niger since Friday, the U.N. refugee agency said on Tuesday, adding to a humanitarian crisis caused by the spread of violence in the region.

The Islamist group first took the town of Bosso near the Nigerian border on Friday in an attack in which 30 soldiers from Niger and two from Nigeria were killed. It was the deadliest assault in Niger by Boko Haram since April 2015.

A UNHCR statement said on Tuesday that civilians fleeing Bosso are mainly walking toward Toumour, about 30 km (18 miles) to the west. Some are continuing on to the town of Diffa and north toward Kabelawa, where a camp for the refugees is already near capacity with 10,000 people.

They are part of a growing crisis in the Diffa region near lake Chad, where Cameroon, Chad, Nigeria, and Niger meet and where Boko Haram has conducted more than 30 attacks this year, according to the United Nations.

In May, the Niger government estimated that there were more than 240,000 displaced people in the region.

“The welfare of these people and others forced to flee the violence in Bosso is of great concern,” UNHCR said. “Insecurity and lack of access have long hampered humanitarian operations in parts of the Diffa region, though Bosso is the only area where we do not implement projects directly.”

Clashes have continued in Bosso in recent days as both sides seek to retain control of the town. Niger troops briefly regained control of Bosso on Saturday morning, according to the defense ministry, but the militants retook it on Sunday night, Bosso Mayor Mamadou Bako said.

Reuters was unable to independently verify who had control of the town on Tuesday.

Boko Haram has been trying to establish an Islamic state adhering to strict Sharia law in northeast Nigeria since 2009. About 2.1 million people have been displaced and thousands have been killed during the insurgency.

(Reporting By Nellie Peyton; Editing by Edward McAllister and Tom Heneghan)