Kenyan police officers have raided a mosque in the port city of Mombasa, the third mosque to be raided this week, as the state continues its hunt for weapons and supporters of al-Qaeda-affiliated al-Shabab fighters in neighbouring Somalia, police have said.

Richard Ngatia, a local police chief, said investigators had found three machetes, a grenade, two 10-litre petrol bombs and a bomb detonator during the operations.

"The mosques have been radicalising youth, training and encouraging them in jihadism. We also recovered a booster used to accelerate explosions ... and literature about jihadism," Ngatia said on Wedensday.

Police have arrested 376 people so far during the raids, but 91 were subsequently released for lack of evidence. One person was killed during the first raids on Monday.

Prosecutors said 158 would be charged with being members of al-Shabab. Police said they were still considering what to do with the other detainees.

Robert Kitur, Mombasa County police commander, told the Reuters news agency that authorities had been gathering intelligence for a long period and it was time to act.

"These operations have started and will go on until all places of worship especially mosques in Mombasa are set free from terrorist and criminal elements," Kitur said. 

The Kenyan government has been battling insecurity and deadly attacks across the country since its troops entered neighbouring Somalia in October 2011 to stem raids on coastal towns. 

Source: Al Jazeera and agencies