Nairobi, Oct 6 (IANS): At least six persons were killed and one injured on Thursday after suspected al-Shabaab terrorists attacked a residential plot in Kenya's Mandera county on the border with Somalia, a media report said.

"We have confirmed six people have been killed and 13 others rescued. The militants used a grenade to break the entrance before they shot at those who were sleeping in there and later escaped from the scene," Xinhua news agency quoted an official as saying.

The militants, who targeted non-locals, struck at 2 a.m. (local time) and shot the tenants arbitrarily, the official said.

The attackers later hurled another grenade that destroyed a building close to the residential plot, after a group of police reservists responded to the attack, the official added.

The police have launched an investigation into the latest incident that has sparked tension in the region.

Mandera Governor Ali Roba noted that the attack came after a lull pg months in the area as a result of intensified police operations.

Security in Mandera remains fragile as al-Shabaab terrorists had crossed over from Somalia and carried out attacks.

Northern Kenya has borne the brunt of grenade and gun attacks in the last four years since Kenya sent troops to Somalia to fight al-Shabaab.