A Kenyan official says police officers killed four suspected extremists at the Somali border, a region hard-hit by recent attacks by the Somali extremist group al-Shabab.

North Eastern Regional Coordinator Mohamud Saleh said Sunday that police killed the men while ambushing a group of about 20 suspected members of a cell of al-Shabab militants on Saturday.

Saleh says the group allegedly was planning an attack on a police station. He says police recovered four rifles and Somali army military jackets.

Al-Shabab, the al-Qaeda affiliate in East Africa, has vowed retribution on Kenya for its troop presence in Somalia.

Kenya deployed troops to Somalia in 2011 to fight al-Shabab, which is waging an insurgency against Somalia's weak U.N.-backed government threatening instability in the region.