U.S. President Barack Obama has informed the Congress he is sending up to 300 U.S. military personnel to Cameroon, as the White House said it was part of a stepped-up effort by Washington to counter the violent sect, Boko Haram.

An advance force of 90 U.S. military personnel has arrived in Cameroon, an administration official said on condition of anonymity.

The forces will be conducting airborne intelligence, surveillance and reconnaissance operations, the official said, adding they would be armed for their own protection.

Obama notified House Speaker, John Boehner, R-Ohio, in a letter. The White House released the letter on Wednesday.

U.S. personnel began deploying on Monday under an arrangement with the Cameroon government. A total of about 300 U.S. service members could be sent.

They will be armed to provide their own protection and security and will stay in Cameroon until they are no longer needed.

Cameroon has been battling Boko Haram militants based in neighbouring Nigeria. The group has vowed to retaliate against Cameroon for backing the Nigerian military’s mission to defeat Boko Haram.

Early this week, two female suicide bombers suspected to be members of the Nigerian militant group killed nine people near the town of Mora in Cameroon’s Far North region.