Police in the Kenyan capital, Nairobi, have defended their operations against the banned Mungiki sect, amid accusation they used excessive force.
Resident have been fleeing the Mathare slum
Spokesman Eric Kiraithe said the police had to use force after officers came under fire in the Mathare slum.
He also confirmed that three more Mungiki suspects had been killed. More than 30 have died this week.
The secretive sect has threatened to step up its war in an anonymous e-mail sent to the media.
Mungiki members are accused of beheading more than a dozen people, including policemen, in Nairobi and parts of the central province in the past three months.
Last week, President Mwai Kibaki warned that Mungiki activities would no longer be tolerated and ordered a shoot-to-kill policy.
Residents have continued to flee Mathare, scene of this week's clashes.
Some 500,000 people normally live in the slum, which is believed to be a Mungiki stronghold.
"We have arrested 250 suspects and the police are faced with a very grim situation where people were prepared to fire back. It is only unfortunate that some of the suspects were prepared to die fighting," Mr Kiraithe said.
KENYA'S SECRETIVE MUNGIKI
Banned in 2002
Thought to be ethnic Kikuyu militants
Mungiki means multitude in Kikuyu
Inspired by the Mau Mau rebellion of the 1950s
Claim to have more than 1m followers
Promote female circumcision and oath-taking
Believed to be linked to high-profile politicians
Control public transport routes, demanding levies
Blamed for revenge murders in the central region
Mr Kiraithe said residents were fleeing because they were afraid that police would not be able to protect them from the Mungiki.
Opposition leader Kalonzo Musyoka asked the government to stop the operations and instead negotiate with the Mungiki leaders.
"It appears to us that clearly they know about them because they have been funding them, why don't they talk to their very own people?" Mr Kalonzo asked.
But an e-mail purported to be from the Mungiki sect and made available to the BBC declares war on security forces and leaders who are supporting the crackdown.
"Kenyans must know, we have never killed indiscriminately, the ones killed have been previously warned. Now the government has changed the rules of engagement.
"You are fighting us as animals and we will become animals," the e-mail reads.
The Mungiki are thought to be militants from Kenya's biggest ethnic group, the Kikuyu.
Some commentators have linked them to politicians wanting to cause unrest and fear ahead of December elections.