* Supporters of cleric suspect police of killing
* Shooting similar to slaying of another imam in 2012
* Muslim leaders say crackdown alienates young people (Adds Muslim rights leader, cleric supporter, context)
By Joseph Akwiri
MOMBASA, Kenya, Oct 4 (Reuters) - Gunmen in Kenya have killed a radical Muslim cleric who had preached a mosque linked in the past to Somali Islamist militants, raising tensions in the port city of Mombasa.
The apparent assassination of Sheikh Ibrahim Omar, who died along with three other men in the same car, follows the killing of at least 67 people in last month's attack on a Nairobi shopping mall claimed by Somalia's militant al Shabaab group.
Omar's associates and some people who attended his mosque said he was the latest victim in a string of extra-judicial killings of Muslims by Kenyan security forces, an allegation denied by the police.
The shooting took place late on Thursday night, just a few hundred metres (yards) from where another firebrand cleric, Aboud Rogo, was shot dead in his vehicle in August 2012 in a strikingly similar attack. Both Kenya and United States had accused Rogo of recruiting and fund-raising for al Shabaab.
"This is no doubt a police execution given what has happened in Nairobi," said 37-year-old Abdul Hassan Omar in Mombasa's rundown Majengo district, where Omar and Rogo both preached. "I will be surprised if Muslims do not protest against this."
Mombasa county police chief Robert Kitur said the police had nothing to do with Omar's killing, but that they would not allow any protests after Friday prayers to lead to unrest.
"We are warning them not to dare because we shall deal with them," Kitur said.
Rogo's death last year unleashed deadly riots in Mombasa's run-down neighbourhoods where he commanded a loyal support base. Anti-riot police patrolled Majengo on Friday and many businesses remained shut.
The assault on the Westgate mall was the worst militant strike on Kenyan soil since al Qaeda bombed the U.S. Embassy in Nairobi in 1998. The raid shocked Kenyans and the world and has raised questions over intelligence failures.
"They (authorities) have panicked because of their own laxity which killed Kenyans at Westgate. Now they are trying to save face by sacrificing innocent Muslims," said Hatib Suleiman, 21, who prays at Omar's Masjid Mussa mosque.
"We are not going to take this lightly."
Al-Amin Kimathi, chairman of the Muslim Human Rights Forum, said Omar had been a student of Rogo and had publicly espoused the hardline ideological beliefs of his former mentor.
Like Rogo, Omar was popular among Muslim youths in Mombasa and along Kenya's Indian Ocean coastline, where many Muslims feel marginalised by the predominantly Christian government.
"With Westgate, emotions are very high and there is public pressure to get results and be seen to be clamping down on terrorism," said Kimathi.
Radicalism among Kenya's Muslims has been a prime concern of the government and the West. But Kimathi said the authorities' response had been heavy-handed, alienating Muslims and serving as a recruitment tool for militants.
The Westgate massacre, he said, provided the security forces the "perfect cover" to continue their crackdown.
"They know public opinion will be on the side of counter-terrorism agencies, no matter how heavy-handed the operations are," Kimathi said. (Additional reporting by Drazen Jorgic and Richard Lough in Nairobi; Writing by Richard Lough; Editing by James Macharia and Alistair Lyon)