Four policemen have been seriously injured in Kenya's coastal city of Mombasa in a grenade attack.
Regional police chief Aggrey Adoli told the BBC the officers were on patrol near the Mombasa Pentecostal Church when their vehicle was hit.
It follows two days of rioting that has left four people dead, including a policeman and two prison guards brought in to help with violence.
The riots were sparked by the killing of a radical Muslim cleric on Monday.
Some of the rioters had accused the authorities of carrying out a "targeted assassination" on Aboud Rogo Mohammed, who was on US and UN sanctions lists for allegedly supporting the al-Qaeda-affiliated al-Shabab in neighbouring Somalia.
However, police spokesman Charles Owino was quoted as saying that al-Shabab killed the cleric in an attempt "to galvanise support among the youth".
The BBC's Jamhuri Mwavyombo in Mombasa says there is a heavy security presence in the city as President Mwai Kibaki has arrived to attend the annual agricultural show.
Two dozen people were arrested on Tuesday in the riots and were charged in court on Wednesday with taking part in an unlawful assembly and in a riot.
They were remanded in custody pending bail hearings.
Our reporter says residents in some suburbs complained on Wednesday of police harassment and beatings after house-to-house searches.
But Mr Adoli told the BBC the searches were justified in order to flush out the trouble makers.
The UN Security Council imposed a travel ban and asset freeze on him in July, saying he had provided "financial, material, logistical or technical support to al-Shabab".
It accused him of being the "main ideological leader" of Kenya's al-Hijra group, also known as the Muslim Youth Centre, which is viewed as a close ally of al-Shabab.
In 2005, Mr Rogo was cleared on murder charges over the 2002 attack on a hotel where Israeli tourists were staying, which killed 12 people.