One man has been killed and more than 200 people arrested during raids on two mosques in the Kenyan city of Mombasa, which police accused of having links with Somalia's al-Qaeda-affiliated al-Shabab fighters
Kenya has been trying to break up fighter networks it blames for a series of attacks on the coast, saying many recruits were inspired by al-Shabab.
Security forces began the operation in the early hours of Monday morning, targeting the Musa and Sakina mosques in the port city.
A 20-year-old man was shot dead by police during the raid on the Musa mosque, after he tried to throw a grenade at officers, Mombasa police chief Geoffrey Mayek said.
"We had information that the group had been planning an attack, and that is why the raid was conducted," Mayek was quoted by the AFP news agency, adding that 201 people had been arrested.
The Reuters news agency, quoting police officials, put the number of arrests at 251.
Mayek said that eight grenades, a pistol, six bullets, machetes, daggers and literature on warfare were found at the two mosques.
Police also said they had seized mobiles and laptops, alongside literature and videos that they said referred to former al-Qaeda leader Osama bin Laden and Kenyan preachers accused of promoting violence.
"These mosques have been notorious for radicalising our youth and recruiting them into al-Shabab," Nelson Marwa, the commissioner responsible for administering Mombasa County, told Reuters.
Civil rights group condemned the raids, saying the security agents were targeting Muslims unfairly, deepening distrust in a Muslim community that already accuses the government in mainly Christian Kenya of sidelining them.
"The police have again defiled the mosques and turned them into camps of violence and have arrested many innocent people and even killed one unfairly," Hussein Khalid, director of Haki Africa, a local rights group, told Reuters.
Businesses in the Majengo area where the mosques are situated were closed as heavily armed police patrolled the neighbourhood on trucks. Past raids have sparked protests.
Western nations have warned their nationals to avoid all but essential travel to Mombasa, a key transport hub as well as an important tourist centre for the country's Indian Ocean coastline.
The city has been hit by bombings and shootings since Kenya troops entered Somalia in 2011 to attack al-Shabab, later joining an African Union force battling the group.