Militant Islamist group al-Shabab says it has killed six Christians in north-eastern Kenya in an attack aimed at forcing them out of the region.

The six were killed in a grenade and gun attack on a residential block in Mandera town, police said.

It was the latest in a spate of deadly attacks targeting Christians in the mainly Muslim region.

In December 2014, al-Shabab killed 38 non-Muslims at a quarry after separating them from Muslim workers.

A few months earlier, 28 people were killed after Muslim passengers were split up from the other passengers.

When al-Shabab killed 148 people in an attack on Kenya's north-eastern Garissa University College in April 2015, the militants reportedly singled out Christians and shot them, while freeing many Muslims.

The latest raid took place in the early hours of Thursday in an area popular with people who came from outside Mandera town, reports the BBC's Ferdinand Omondi from Kenya.

Mandera County Governor Ali Roba confirmed that six people had been killed and one seriously wounded in the raid on a public works site in the town.

Security forces responded quickly, managing to save 27 other people, he added in a tweet.