One person was killed in the Kenyan coastal city of Mombasa on Sunday after youths rioted to protest against the killing of an alleged Islamist militant.

Unidentified gunmen shot and killed Hassan Guti on Saturday as he was driving in the city with his wife and niece. Riots broke out on Sunday after his burial.

Police officially denied involvement in the killing, but sources within the Force said Guti was killed by the elite Anti-Terrorism Police Unit.

Kenya’s coastal region, a tourist hub where most of the country’s Muslims live, has suffered a series of bomb attacks in recent months blamed on Islamists tied to Somalia's militant al-Shabaab group.

Police said Guti was linked to the shooting of a senior police officer in Mombasa in August and was also facing a murder charge for a separate incident.

Following Guti’s burial, youths started attacking people in the Majengo area but police managed to contain rioting there, said Robert Kitur, Mombasa's police chief.

"They stabbed four people and one of them died. We have arrested 20 youth so far and will charge them in court tomorrow,” he said.

The attacks against residents appeared to be indiscriminate.

Police fired teargas to disperse the youths, who witnesses said attacked motorists with stones and robbed businesses.

"They were throwing stones at police and vehicles, and looting from shops in Majengo. We had to close down our shops quickly,” Islam Juma, who runs a clothes shop in the area, told Reuters.

Local rights groups condemned Guti's killing.

"It is becoming normal for people to be shot and killed in Mombasa, and nobody is ever arrested for this,” said Hussein Khalid, director of Haki Africa, a rights group. "What is wrong with our security agents?”

Last week, pro-government Muslim cleric Sheikh Salim Bakari Mwarangi was shot and killed in the city by unknown gunmen who escaped on motorbikes.

Sheikh Juma Ngao, chair of the Kenya Muslims National Advisory Council, said it had become dangerous to be Muslim.

"If you are a radical Muslim you are targeted by the government. If you are a moderate one, the radical Muslims will target you because they see you as a traitor, so what do we do?” Ngao said.

Agencies