MANDERA, Kenya - Kenya police confirmed that at least 36 people were killed early Tuesday morning in an attack by suspected Al-Shabaab militants in northern Kenya.

Mandera County Police Commander Noah Mwivanda said the construction workers were killed at 1 a.m. local time Tuesday (2200 GMT Monday) by a group of suspected Al-Shabaab gunmen while sleeping at a quarry at Koromey, about 20 km from Mandera town bordering Somalia.

"So far we have counted 36 bodies at the scene. The attack is similar to the one in which 28 people were killed in a bus last month. We have not yet established the motive behind the latest attack," Mwivanda said.

He said initial investigations have revealed that all the construction workers, all of them men, were killed after being ambushed by heavily armed militants.

"The deceased were lined on the ground before they were shot at close range. Four bodies were beheaded while others bore bullet wounds on their heads and chests," said a resident.

He said all the deceased were non locals who were working at a local construction site in the restive region. No group has claimed responsibility.

Last month, Al-Shabaab claimed responsibility for the bus killings through its radio station in Somalia, saying it was in retaliation for the raids carried out by Kenyan security forces earlier in November on four mosques in Kenyan coastal city Mombasa.

Kenya has witnessed several attacks since 2011 when it participated in fights against the Al-Shabaab militants in Somalia.