LONDON — There are growing signs that Britain has become the European center of Islamic terrorism, with claims by a leading British Islamic radical that some 50 potential suicide bombers are currently in the country and warnings that it could become the target for suicide attacks.

At the same time, British intelligence is said to have known about the radical views of the two Britons who attacked the Tel Aviv bar Mike's Place last week, but failed to keep them under surveillance because they were not considered potential terrorists.

Leading British Islamic radical Hassan Butt, who styles himself a recruiter of volunteers for the "Islamic holy war," said he had been approached for guidance on how to carry out "martyrdom operations" in Israel.

He said he knew Assif Mohammed Hanif, who blew himself up outside Mike's Place, and Omar Khan Sharif, whose bomb failed to detonate, but warned that they were just the first of a significant number who are preparing to conduct such attacks.

"The number is getting close to 50," Butt told the Sunday Times. "They are aged 17 to their late 30s. They are contacting me about organization." He believes "about 20" are "absolutely serious." Most, he said, live in Britain but have family roots in Pakistan, India and Bangladesh.

"They are waiting for the right time, the right people," he said. "You don't just do it as individuals, you do it as an organization. It's about screening them, testing them, making sure they are sincere. Then, when it's right, believe me, they'll all be used."

Butt, who was questioned by police last November, warned at the time that he knew British-based fundamentalists were preparing to carry out suicide attacks abroad. He also accurately claimed that scores of Britons had gone to fight with the Taliban in Afghanistan, introducing some of them to journalists.

Six people in Britain are currently being questioned about the Tel Aviv attack by anti-terrorist investigators, who are said to be examining cell phone records, personal computers and religious literature that were seized at the homes of the bombers.

Among those who have been arrested are Tahira Sharif, 26, the failed bomber's wife, his sisters Parveen and Nasreen, his brother Zahid Hussein Sharif, Tahira's brother Amar Jazira, and Zahid Ahmed, a family friend.

Meanwhile, the Sunday Telegraph reported that British intelligence knew Hanif and Sharif had links to al-Muhajiroun, a group that aims to create a global Islamic state, but concluded the two were on its fringes and were not placed under constant surveillance.

It is not known whether their movements were tracked as they visited foreign countries, including Syria, or whether their identities were passed to intelligence services in Israel or America.

The Syrian-born head of al-Muhajiroun in Britain, Sheikh Omar Bakri Muhammad, said he knew the Tel Aviv bombers as students and had acted as their spiritual adviser, but he denied prior knowledge of the attacks.

Bakri, who currently lives in north London, told the Sunday Telegraph that Sharif attended six two-hour sessions in Derby, ending on April 14, just over two weeks before the Tel Aviv bombing.

Sharif had asked Bakri to become his spiritual "companion," a status accorded to extreme fundamentalists who are willing to suffer, including imprisonment and death, for their faith. But Bakri said he declined the offer because he was too busy, and he denied encouraging Sharif to carry out the attack.

According to reports here, the Mossad is also probing links between the bombers and al-Muhajiroun. Israeli security sources are quoted as saying the men used an explosive not previously employed in suicide attacks. They believe Hanif and Sharif were trained by Hezbollah. in Syria and instructed by the head of Hamas' overseas operations.