A moderate Kenyan Muslim religious leader, who supported government efforts to stamp out rhetoric of armed al-Shabab group, has been killed by unknown assailants, according to Kenyan police.

Sheikh Salim Bakari Mwarangi was killed on Wednesday while returning home from evening prayers at a mosque in the Likoni area of Mombasa, the local police chief said.

"Gunmen on a motorbike slowed down, shot at him and sped off," Robert Kitur said.

"Police have launched an investigation and manhunt for the attackers."

Kenya's coastal region, a tourist hub where most of Kenya's Muslims live, has been hit by a spate of bomb attacks over the past months blamed on al-Qaeda-linked al-Shabab group based in Somalia.

Kassim Bakari, a relative of Mwarangi, said the slain man had received death threats and feared for his life, according to the AFP news agency.

"People were calling him saying they are looking for him to kill him," Bakari said.

"But he was a preacher who liked peace and always preached peace."

Moderate stance

Haki Africa, a local Muslim rights group, said Mwarangi was a peace activist and that his killing may have been tied to his moderate stance.

"He was a member of the Mombasa peace committee and was helping the government a lot in dealing with radicalisation and guiding Muslim youth towards the right path," Francis Auma, the organisation's programmes coordinator, was quoted by Reuters news agency as saying.

"He may have created enemies, but the police will establish the truth in their investigations."

Mwarangi is just the latest Muslim leader to fall victim to violence in the region.

In June, Sheikh Mohammed Idris, chairman of the Council of Imams and Preachers of Kenya, was killed by assailants at a mosque in the same area.

Muslim activists said at the time he was among 21 other renowned religious preachers who had either disappeared or been killed in a similar manner since 2000.

Kenya is trying to break up fighter recruitment networks in its Muslim community in an effort to end attacks it blames on al-Shabab and its sympathisers, who have pledged to punish Kenya for sending troops to Somalia to fight them.