Kenyan police say a hand grenade has ripped through a church in the capital, Nairobi, wounding three children.

Unconfirmed reports say one child later died after Sunday's attack.

Similar deadly attacks against churchgoers have taken place in Kenya on recent Sundays.

There have been no claims of responsibility for the attacks. However, authorities say the attacks appear to be in retaliation for the Kenyan army sending troops across the border into Somalia to fight al-Shabab militants.

The group, linked to al-Qaida, abandoned its last stronghold in Somalia on Saturday, vowing to carry out attacks against Kenyan and African Union forces fighting against al-Shabab.