Unidentified gunmen have killed a Kenyan Muslim cleric who was accused of supporting Somali militant group al-Shabab.

Witnesses say Aboud Rogo Mohammed was shot dead Monday while driving a van in the port city of Mombasa.

VOA's Swahili Service reports that protests against the killing broke out soon afterward, with demonstrators blocking off Mombasa streets.

Aboud Rogo Mohammed was placed on a U.S. sanctions list last month for allegedly recruiting fighters and raising money for al-Shabab.

The U.N. Security Council placed its own travel ban and assets freeze on the cleric, saying he used an extremist group, Al Hijra, as a way of recruiting Swahili-speaking Africans to fight in Somalia.

Al-Shabab is fighting to overthrow Somalia's U.N.-backed government. The militant group is known to have supporters in Kenya, which has a large Somali immigrant community.

Kenyan forces entered Somalia last October to fight al-Shabab, and have since joined the African Union peacekeeping force in the country.