British Prime Minister Tony Blair says the Muslim community needs to stand up against radical clerics who are enticing young British Muslims to support terrorist movements.

Relations between British Muslims and the broader society are under close scrutiny, following police raids this week that netted half a ton of potentially explosive fertilizer and the arrest of eight men believed to be British Muslims of Pakistani origin.

Lawyers at a Muslim conference this week said 548 British Muslims have been arrested as terrorist suspects since the 2001 attacks in the United States, but only 91 have been formally charged, and of those, only 15 have been convicted.

Prime Minister Blair addressed the matter at a news conference, Thursday. He rejected suggestions that the statistics prove police are heavy-handed toward Muslims. And he said the public, including most Muslims, demand strict anti-terrorist vigilance.

"This particular form of terrorism that we are dealing with is based on what I think the vast majority of Muslims would accept is a perversion of the true faith of Islam," the prime minister said, "and therefore, necessarily and obviously, many of those that will be questioned will be Muslims. But that is not in any shape or form a disrespect to the vast majority of the Muslim population here."

Mr. Blair also said the time has come to confront radical Islamic clerics who are attracting young Britons to join terrorist movements.

"We have to challenge these people and we have to take on their ideology, their rhetoric, their extremism and their fanaticism, and we have to defeat it," he said. "There is going to be a limit, however, to what a political leader in my position can do in respect to that. It also has to be led within the Muslim community itself."

The prime minister repeated his gratitude to the moderate Muslim Council of Britain, which has sent a letter to more than 1,000 clerics urging them to report any suspected terrorist activity at their mosques.

Before the arrests this week, there were several other high-profile terrorism cases involving British Muslims, including an attempt to blow up a U.S.-bound jetliner and a suicide bombing in Israel. Also, several British Muslims were captured on the battlefields of Afghanistan fighting in support of the Taleban in 2001. Four of them remain detained by the U.S. military.