His arrest started as an invitation to coffee and ended three days later, when he walked out of a jail cell.

Ahmed Kafaween, a longtime leader of Jordan's most influential Islamic group, arrived at the provincial government building in the southern city of Karak one afternoon this month after being summoned for a chat by the police chief, who had kindly provided an escort.

"On August 20th, did you say during Friday prayer that the al-Aqsa mosque in Jerusalem was in danger of being destroyed by the Jews and that the United States supported its destruction?" Kafaween recalled being asked by an Interior Ministry agent, who was reading from a file. "Did you denounce other Arab governments for doing nothing about it?"

Kafaween said yes, then refused to sign a pledge never to do so again. He was jailed for three daysas part of a nationwide roundup of 38 Islamic leaders, activists and clerics on Sept. 9 for allegedly violating a law prohibiting political commentary inside mosques.

"It was a way to stop our tongues," said Kafaween, 57, a leader of the Muslim Brotherhood and a former member of parliament. "But we can't be made to keep our mouths shut."

The detentions signal a rare crackdown by one of the Middle East's most tolerant governments, now facing uncharacteristically strident criticism from a popular Islamic movement over its alliance with the United States and diplomatic relations with Israel. As violence worsens in Iraq on this small desert kingdom's eastern border and in the West Bank in the opposite direction, Jordan's traditionally moderate Islamic activists have intensified their rhetoric denouncing the government, which has responded by enforcing strict limits on free speech.

The criticism poses a challenge to King Abdullah as he pushes Western-style reforms in a country buffeted by the anger that the Iraq war has stirred in the region. Largely as a reward for Abdullah's support for the war, U.S. military and development aid to Jordan nearly tripled in 2003, to more than $1.5 billion. But that economic assistance has compromised the government in the eyes of an increasingly angry population of 5.5 million.

Signaling his concern, the king wrote an open letter to his prime minister in July that called for new preaching guidelines that "take into consideration the new variables and emphasize the compassion of the Islamic religion."

But in recent weeks, elderly Islamic leaders and members of a younger, more radical generation have stepped up criticism of government policies, delivering much of it from inside the country's well-monitored mosques. Many of the critics are young, unemployed and attracted to the social and political changes promised by Islamic politics, including a more democratic government favored by the movement's main organization, the Muslim Brotherhood.

During Friday sermons, speakers have called the monarchy "an infidel government" for its support of the United States, lashed neighboring Arab governments for their passivity and called for an end to a decade-old agreement normalizing relations with Israel, according to government officials familiar with the arrests. Other speeches have allegedly questioned the legitimacy of the monarchy.

"There have been violations of the law in the past, but they never criticized in this way," said Ramadan Rawashdeh, an adviser to Prime Minister Faisal Fayez. "They are a political party, with a political headquarters, so give your political lessons there. We think doing so in the mosques is against our religion and against the law."

Hamza Mansour, secretary general of the Islamic Action Front, the Muslim Brotherhood's political arm, said the scope of the recent arrests, some of which were made during night raids on private homes, makes them more significant than others. He said the targets, including a former cabinet minister, five former members of parliament and a regional political official, were symbols of the movement.

The former minister of holy places and Islamic affairs, Ibrahim Zaid Kilani, suffered a mild heart attack when police entered his house, and he remains hospitalized. All of those arrested have since been released. Most of them were required to sign pledges to refrain from expressing criticism in the mosques.

"The harassments are not new, but they have increased greatly because of international pressure," said Mansour, who asserted that the monarchy had typically moved hardest against the brotherhood at times when Jordan was aligned with an unpopular U.S. policy. "By doing this, they ignore the people who are moderate and give opportunity to those who are not. The alternative is much more extreme than we are."

Unlike in Egypt, where the Muslim Brotherhood was founded in 1929, Jordan's branch has been a mainstream political movement, used by the monarchy in the past to offset the influence of Arab nationalist and communist parties.

In 1989, the brotherhood won 23 of 80 parliamentary seats, more than any won by Jordan's stunted and disorganized political parties, in the country's first free elections. The showing alarmed the government, which changed election laws to favor the monarchy's rural tribal base.

In 1993, the brotherhood -- which had by then formed the Islamic Action Front -- won only 16 seats and boycotted the following elections in protest. After a pledge from Abdullah to reform election laws again, the party participated in the 2003 vote, winning 17 seats -- the largest single group in what is now a 110-member parliament.

The government has adopted measures to regulate the brotherhood's political influence in the mosques. Only clerics licensed by the Ministry of Holy Places and Islamic Affairs are allowed to deliver Friday sermons in the country's roughly 3,000 mosques, and they must adhere to regulations that prohibit criticism and political content.

The government pays licensed clerics as much as $450 a month, largely ensuring their loyalty to the monarchy. Informants file reports to the security services and the religious ministry on the contents of Friday sermons and the subsequent "lessons" delivered by clerics and activists, according to government officials. Most of those who were arrested this month were not licensed or had been suspended from preaching by the government.

"We have to go through the procedures of enforcing the rules in this manner," said Fouad Nejdawi, a ministry spokesman, "because otherwise they may do something worse than just speak. The consequences may be very high."

Abdul Latif Arabiyat, 57, was among the brotherhood members elected to parliament in 1989. He was selected speaker of the lower house and pushed for more political freedom and broader elections. He said he always viewed himself as a partner of the monarchy, never its opponent.

Arabiyat criticized the recent Friday sermons as unfair and unproductive. But he said arresting brotherhood members for speaking out may only push the problem into the shadows.

"We are facing a very hot situation in the region, and you will find people saying things out of character with the past," he said. "It is partly our job to control this. But we are also telling the government to give some kind of window to the people, so they can breathe and express themselves. Otherwise, their spirit will be destroyed."

On a warm evening this week in Amman, the capital, Kafaween appeared undaunted by his recent arrest. He was the keynote speaker at an event marking the fourth anniversary of the Palestinian uprising, and he delivered an explosive, furious speech that criticized the United Nations, Russia, Israel and the United States.

More than 500 people gathered at the headquarters of Jordan's professional association of engineers to hear Kafaween, who waved his plastic glasses in his left hand and clutched the lectern in his right throughout his 20-minute speech.

Most of those inside the hall were graying men like Kafaween. But some of the seats were filled by young men in Che Guevara T-shirts, whose chants calling for the return of "Muhammad's army" echoed in the smoky room.

"Palestine is occupied, Iraq is occupied and Sudan is in danger," Kafaween shouted. "So take care, Arab people, and wake up. God, witness that I have told them."

Ahmed Kafaween, center, a leader of the Muslim Brotherhood, was detained for three days after using a mosque as his platform for political commentary.