Gracious and fluent in English, which he said he learned while growing up in South Africa, the bearded religious scholar welcomed a foreign visitor onto the well-kept grounds of the Jamiat-ul-Uloom Islamiya, one of the country's largest Sunni Muslim seminaries.

"I will answer all of your questions," said the scholar, Ismail Mulla, as an attendant poured cups of sweet, milky tea. Nearby, students in prayer caps strolled across a white-marble courtyard, hunched over religious texts in sweltering classrooms or sat cross-legged on carpets for a midday meal of mutton and flatbread.

As Mulla described it, the institution has one purpose: to prepare young men for a life of propagating Islam. "We teach basically the Koran and the Sunnah" -- the sayings of the prophet Muhammad -- said Mulla.

But the placid setting belied what some analysts and police investigators have said is a link between some people at the seminary and Islamic extremists responsible for a wave of attacks against foreigners, senior government officials and religious minorities over the last few years.

The seminary, or madrassa, had been led by Mufti Nizamuddin Shamzai, until he was gunned down in front of it on May 30. Shamzai, an associate of Osama bin Laden and Taliban leader Mohammad Omar, publicly urged his followers to wage holy war against U.S. forces in Afghanistan. A number of former students at the madrassa are being held at the U.S. detention facility in Guantanamo Bay, Cuba, according to a May 4 report in the English-language newspaper Dawn.

Certain students or graduates of the madrassa have been implicated in an escalating series of attacks on members of the minority Shiite Muslim population, including the suicide bombing of a Shiite mosque that killed 23 worshipers on May 7, police said. That bombing marked the opening salvo in a surge of extremist violence -- including a brazen daylight attack Thursday on the motorcade of a senior army general -- that has killed more than 70 people in Karachi, the country's largest and most economically important city, in little more than five weeks.

Mulla, who was designated to speak for the organization, dismissed charges that the school is linked to terrorist groups. "Right next to us is a police station, so these are all lies," he said.

More broadly, the bloodletting has cast a spotlight on the nexus between some of Pakistan's estimated 10,000 madrassas and armed extremist groups. These groups once operated with the backing of the country's security services but more recently have targeted the government of Gen. Pervez Musharraf, Pakistan's president, in response to his support for the U.S.-led war on terrorism.

The government has not followed through on pledges to regulate the madrassas -- including plans to require the teaching of secular subjects such as math and science -- and to control their funding, some of which comes from radical sympathizers in Saudi Arabia and other Arab countries. Musharraf is reluctant to enforce the regulation, analysts said, because he wants to remain on good terms with radical Islamic political parties. The parties, along with the army, constitute a vital part of his power base, even if he has little use for their ideology.

"This government has done nothing to curb religious extremism in Karachi," said Samina Ahmed, who heads the Islamabad office of the International Crisis Group, a Brussels-based nonprofit that specializes in conflict resolution. "The madrassas are flourishing."

Government officials said most madrassas do not promote extremist violence. They described them as an important part of Pakistan's social safety net, providing free schooling and often room and board for hundreds of thousands of impoverished young people.

"If there are one or two rogue elements in any institution, it certainly doesn't seem prudent to close down the entire madrassa," said Interior Minister Faisel Saleh Hayat said in a telephone interview from Islamabad. "Such rogue elements can be found in any institution."

Hayat rejected criticism of the government on regulating the madrassas, saying the new federal budget will address modernizing their curriculum.

But the madrassas are likely to resist.

"Why do we have to change our curriculum?" asked Mulla, the Islamic scholar, noting that his madrassa -- while concentrating on religious studies -- already requires three years of schooling in math, science, English and social studies. In any case, he added, "do we go to the universities and say, 'You're teaching engineering, now you have to teach the Koran?' It's our right. Why should they interfere?"

Over the last two decades, military and civilian governments have encouraged the growth of the madrassa system, which has provided recruits for extremist groups allied with Pakistan's security forces. Many of the former students have become fighters in Afghanistan and in Indian-held Kashmir.

As part of his policy U-turn after the Sept. 11, 2001, terrorist attacks on the United States, Musharraf has taken a number of steps to sever the ties between the government and extremist groups, some of which were banned in 2002. By all accounts, however, most madrassas have yet to change their way of doing business, and continue to churn out thousands of religious zealots yearly.

The Jamiat-ul-Uloom Islamiya is a case in point.

Founded in the 1950s, the madrassa consists of a large walled compound whose red-painted minarets overlook a busy commercial thoroughfare in the Binori neighborhood of this overcrowded port city of more than 10 million people. The madrassa serves roughly 10,000 students, most from Pakistan but some from other countries such as Indonesia, Thailand and Malaysia, according to Mulla, 47, who is of Pakistani origin. He studied at the madrassa and returned here from Durban, South Africa, seven years ago to teach. The students, who range in age from 5 to 40, are schooled in the fundamentalist Deobandi tradition, which is similar to the austere Wahhabi version of Islam practiced in Saudi Arabia.

"Every Muslim is a fundamentalist, and he should be," said Mulla, a tall, sinewy man with a stiff beard. "They should be practicing their religion to the teeth."

Though Mulla said the madrassa has no formal relationship with extremist groups, the late rector, Shamzai, made no secret of his sympathies. During the early 1990s, Pakistani intelligence officials said, Shamzai helped launch Harkat ul-Mujaheddin, which provided fighters for the insurgency against Indian forces in Kashmir and subsequently was blamed for the murders of five Western tourists in the disputed province. The leader of the group, Maulana Fazlul Rahman Khalil, was his former student at the madrassa.

In a 2002 interview, Shamzai boasted of his ties to another former student, Maulana Masood Azhar, a radical cleric imprisoned by Indian authorities and released after his followers hijacked an Indian Airlines jet to Kandahar, Afghanistan, in late 1999. A few months after that, Shamzai appeared with Azhar at the Karachi Press Club when Azhar announced the founding of Jaish-e-Muhammad, which was implicated in the December 2001 attack on the Indian Parliament complex in New Delhi and has been branded a terrorist group by the United States.

A soft-spoken man who died at 75 , Shamzai said in the 2002 interview that bin Laden had been "kind enough" to invite him to his son's wedding in Kandahar in 1998. Shamzai also considered himself a friend and admirer of Omar, the fugitive Taliban leader, according to Mulla. Following the U.S.-led invasion of Afghanistan, Shamzai issued numerous fatwas, or religious edicts, urging Muslims to rush to the aid of the Taliban.

"We support anybody that holds the banner of Islam," Mulla said. "We are all Taliban. You can say that."

The madrassa has also been accused of fostering violence against minority Shiite Muslims. One of its more notorious former students, for example, was Azam Tariq, the head of the anti-Shiite group Sipah-i-Sahaba, who was assassinated in last October in Islamabad. At the time of his death, Azam had 28 criminal cases pending against him, 18 of which involved sectarian violence, according to Muddassir Rizvi, an analyst at the International Crisis Group.

Recently, police have traced the May 7 bombing of the Hyderi mosque, a sandstone structure on the grounds of a colonial-era school, to a student at the madrassa, Qari Ghulam Murtaza. Although he had not completed his studies, Murtaza, in his early twenties, often led prayers at the Quba mosque in Karachi's Baghdadi district, where he recruited and "brainwashed" the young police trainee who carried out the suicide bombing, according to a senior investigator.

Another investigator described Murtaza as "very close" to Shamzai.

Qari Ahmad, the imam of the mosque, a simple structure whose main entrance opens onto a litter-strewn alleyway, said in an interview this week that Murtaza, who has since disappeared, went to Afghanistan twice to wage holy war against U.S.-led forces there. But Ahmad said that if Murtaza harbored any ill feelings toward Shiites, he kept them to himself. "I have no idea why he did it," Ahmad said. "I've never heard anything against Shiites here."

The Hyderi bombing set off a wave of violence that is still reverberating here. Three weeks after the attack, in an apparent act of retaliation, gunmen firing assault rifles from a car and a motorcycle killed Shamzai as he left his apartment across the street from the madrassa. The killing took place at about 7:30 a.m., triggering riots by Shamzai's students and followers.

A day later, a suicide bomber walked into another Shiite mosque less than a mile from the madrassa, detonating a blast so powerful that it split the concrete dome overhead. Sixteen worshipers died.

Mulla, the madrassa spokesman, said that if Murtaza was involved in the first bombing, "it wasn't because of us." In any case, he said, the school should not be held responsible for the actions of individuals. "If he's part of any organization, I can't do anything about it."

Pakistani police arrest a protester at a strike in Karachi on June 4, during a wave of militant violence in Pakistan's largest city. Mufti Nizamuddin Shamzai, a senior Sunni cleric, was killed in Karachi on May 30. A computer- enhanced sketch of a suspect in the killing of Shamzai.