At least 36 people were killed in a suspected al-Shabab attack on a quarry in northeastern Kenya early on Tuesday, according to local media reports. Gunmen reportedly opened fire at Christians after separating them from the Muslims, BBC reported.

The incident reportedly took place in the village of Kormey, about 9 miles from Mandera, close to the border with Somalia, an area from where the al Qaeda-affiliated militant group operates. Nearly 20 militants reportedly attacked the workers while they were sleeping in their tents. A witness told Reuters that four of the victims were beheaded by the attackers while the rest were shot in the head.

"Our team is on the ground undertaking assessments of the attack," the Kenya Red Cross said Tuesday.

The latest attack is reportedly being linked to an al-Shabab raid last month that claimed the lives of 28 people. The Islamist militant group had ambushed a bus heading from Mandera to the capital city of Nairobi on Nov. 22, and targeted non-Muslims after separating them from the Muslim travelers. The group reportedly claimed responsibility for the bus attack stating that it was in response to police raids conducted on mosques in November in Mombasa, Kenya’s second largest city.

The November attack was condemned by Secretary-General Adan Wachu of the Supreme Council of Kenya Muslims, who said that the attack "was not conducted by Muslims. They were conducted by criminals. Islam does not advocate for the killing of innocent people."

After the attack on the bus, Kenya’s military had claimed that it had killed more than 100 al-Shabab militants and destroyed their camp in Somalia.

Al-Shabab has launched several attacks in Kenya after gaining prominence in 2011. The militant group has also carried out several retaliatory attacks after Kenyan soldiers targeted the group’s hideouts in Somalia.