Muslim cleric Abubakar Shariff speaks during an interview in Kenya's coastal city of Mombasa in this October 5, 2013, photograph. Shariff was killed on April 1, 2014. Picture: Thomas Mukoya

Nairobi - Kenya must carry out a thorough investigation into this week's murder of a firebrand Muslim cleric in the port city of Mombasa or else risk an escalation of religious violence, Human Rights Watch said on Friday.

Abubaker Shariff Ahmed, better known as Makaburi and a vocal supporter of Osama bin Laden and al-Qaeda, was gunned down in the strategic city on Tuesday.

Prior to his death, he had accused Kenyan security forces of seeking to kill him.

He was also the third hardline Kenyan Islamist to be killed in Mombasa in as many years.

“Gunning down clerics in the streets is only making a bad situation worse,” said Leslie Lefkow, deputy Africa director at Human Rights Watch.

“The authorities need to put an end to this cycle of violence, and they should start by finding out who is behind these killings and prosecuting them.”

The rights group said the killing of Makaburi and other Islamists “appear linked to accusations by authorities that they were involved in terrorist activities”.

Makaburi was also on UN sanctions lists and accused of being a “leading facilitator and recruiter of young Kenyan Muslims for violent militant activity in Somalia”, and of having “strong ties” with al-Shabaab leaders.

The cleric, who was in his 50s, had also openly praised the suicide commandos who stormed Nairobi's Westgate mall in September last year, massacring at least 67 people in a four-day siege that was carried out in retaliation for Kenya's intervention in Somalia to fight the al-Shabaab.

In August 2012, radical preacher Aboud Rogo Mohammed was also gunned down, and in October last year his successor, Sheikh Ibrahim Ismail, met the same fate on a road near Mombasa, again sparking riots.

“The police have failed to investigate these killings,” Human Rights Watch said, adding that Kenyan police have regularly responded to militant activity with abuses against ethnic Somalis. - AFP