The Islamic Resistance Movement, the militant Palestinian organization responsible for some of the bloodiest attacks against Israel and its citizens, has for years operated more or less openly in Jordan.

Tolerated by the late King Hussein, members of the group, known by its initials as Hamas, maintained offices around Amman, the Jordanian capital, granted interviews, issued statements and went about their business. Their understanding with Jordanian authorities was that they were free to express their views--including advocating terror--and associate with whom they chose, as long as they did not involve themselves in violence.

On Monday that changed.

In a swift, sudden crackdown, Jordanian police raided and closed several Hamas offices in Amman, arrested 12 activists and issued arrest warrants for four senior Hamas figures, at least three of whom are believed to be traveling in Iran. Jordanian authorities said they had discovered that the offices were fronts for a "non-Jordanian group" to conduct illegal activities.

The crackdown is perhaps the boldest move yet in the six-month-old rule of King Hussein's eldest son and successor, King Abdullah. It is the latest setback for Hamas, a group violently opposed to the Middle East peace process whose ability to carry out terrorist shootings or bombings seems to have diminished in the past few years.

Since the Israelis and Palestinians renewed their land-for-peace deal at the Wye River Plantation on Maryland's Eastern Shore last fall, Yasser Arafat's Palestinian Authority has repeatedly arrested or detained Hamas activists in the Gaza Strip and West Bank. Now, with negotiations between Israel and the Palestinians apparently poised to move forward after a long period of inertia, the Jordanians have signaled that they, too, will take tough measures.

"Since the hawks in Hamas have blocked the peace process [through terror acts], gradually the Jordanian authorities have come to the conclusion that such acts are against their national interests," said Menachem Klein, a scholar at Israel's Bar-Illan University.

Arrest warrants were issued for Khaled Meshal, head of the Hamas political bureau, who was the target of a bungled Israeli assassination attempt in 1997; Hamas spokesman Ibrahim Ghosheh; and Mousa Abu Marzook, a top Hamas leader. They were believed to be in Iran. The whereabouts of a fourth leader being sought, Mohammad Nazal, the group's official representative in Jordan, were not known.

The founder and spiritual leader of Hamas, Sheik Ahmed Yassin, reacted to the crackdown with alarm. At a news conference in Gaza City, he condemned the Jordanian action and characterized it as an attempt to appease Israel and the United States two days before a visit to the region by Secretary of State Madeleine K. Albright.

"What happened in Jordan is part of a U.S. plan to press Hamas to join the peace process, and of course we see that process as an attempt to liquidate the Palestinian cause," Yassin said. He urged Abdullah to halt the crackdown in the name of "deepening brotherly ties with Hamas."

Analysts speculated that Jordan may have chosen this moment to move against Hamas because its leaders are out of the country and their arrests would not be turned into causes celebres. Several are well known in Jordan, particularly Meshal, who became a celebrity when agents of Mossad, Israel's foreign intelligence service, tried to kill him by poison injection two years ago on the streets of Amman.

Marzook--well dressed, immaculately groomed and apparently well-off--is a Yassin protege and also a well-known figure in Jordan. He lived for 15 years and had permanent resident status in the United States, where he was arrested by federal officials in July 1995 at the request of the Israeli government, which accused him of raising funds for terrorist activities.

Held in a federal penitentiary in Manhattan for nearly two years, he was deported to Jordan in May 1997 when Israel dropped its request for his extradition. In an understanding with King Hussein, he agreed not to engage in illegal activity as long as he lived in Amman.

Ghosheh, the spokesman, is a slight, soft-spoken and affable man who speaks English well. Despite his moderate manner, his views are as militant as those of the others. This spring, he sharply criticized Yassin for taking part for the first time in a meeting of the Palestine Liberation Organization's central committee. He said Hamas could not support sitting down with mainstream Palestinian groups that are on record as supporting the Middle East peace process.

CAPTION: Jordan has issued arrest warrants for four leading Hamas officials: from left, Meshal, Marzook, Nazal and Ghosheh.