A police report says five Kenyan police officers have died after their armored personnel vehicle ran over an improvised bomb.

The report seen by The Associated Press says the vehicle belonging to the Rural Patrol Border Unit in Mangai in southern Kenya had been going to refuel when the bomb exploded.

The report says seven police officers were in the vehicle and two officers cannot be traced.

The al-Shabab extremist group claims killing seven officers in the incident, according to the SITE Intelligence Group, which monitors such groups.

This brings to 17 the number of Kenyan police killed in the last three weeks in similar attacks. The Somalia-based al-Shabab has claimed them all.

Al-Shabab has vowed retribution on Kenya for sending troops to Somalia in 2011 to fight the extremists.