British Prime Minister David Cameron says the rioting that has gripped the country for much of the past week is not about politics or protest, but is the result of a culture that “glorifies violence.”

Mr. Cameron made his comments at an emergency session of parliament on Thursday. He said the British government “will not allow a culture of fear to exist on its streets,” warning looters that they will be tracked down and prosecuted.

Earlier Thursday, British police began raiding houses in London in connection with the riots. Deputy Assistant Commissioner Steve Kavanagh says officers began knocking on doors to arrest people across the city. He says more than 100 arrest warrants will be served in the “coming hours and days.”

Police have arrested more than 1,100 people since the riots began on Saturday. The violence was originally touched off by the police shooting death last week of a 29-year-old man in London's economically depressed Tottenham neighborhood.

On Thursday, Mr. Cameron said he was considering interfering with electronic devices and websites that rioters have used to coordinate their activity, saying the government is studying “whether it will be right to stop social media when they are being used to plan criminality and violence.”

Britain had its first calm night Wednesday after four straight nights of riots. Police and witnesses reported just minor incidents as thousands of riot police filled the streets of London, Manchester, Liverpool, and Birmingham.

Mr. Cameron has also also faced criticism over his plan to reduce the police budget by 20 percent. On Wednesday, London Mayor Boris Johnson criticized the proposed cuts, saying the riots do not allow for “substantial cuts” in police numbers. Mr. Cameron previously said that the cuts will not “reduce the amount of visible policing.”

Hundreds of youths — many saying they are sick of unemployment and cuts in government help — have burned buildings and cars, looted stores, smashed windows, and attacked police.

Birmingham police opened a murder investigation Wednesday when a car ran over and killed three men apparently while they tried to protect their neighborhood from looters. Police have a suspect in custody.