Al-Shabab fighters have stormed a military base in Kenya’s Lamu county used by both United States and Kenyan military personnel, a government official and the armed group said.

“There was an attack but they have been repulsed,” Irungu Macharia, Lamu Commissioner, told AFP news agency.

It was unclear whether there were any casualties following the dawn attack by the al-Qaeda-linked group.

“The Mujahideen fighters covertly entered enemy lines, successfully stormed the heavily fortified military base and have now taken effective control of a part of the base,” the group said in a statement.

The armed group said the raid resulted in “severe casualties on both American and Kenyan troops stationed there.”

The attack underscores the resilience of al-Shabab, which has maintained a campaign of deadly bomb and gun attacks despite being ejected from their bases in the Somali capital, Mogadishu and other areas years ago.

The group also carries out attacks in Kenya, which sent thousands of its troops into Somalia to fight al-Shabab.