Jordan arrested three leaders of the Islamic Resistance Movement, Hamas, today after they returned to Amman from Iran in an open challenge to the Jordanian government and its recent crackdown against their organization.

Two Hamas officials, Khaled Meshal and Ibrahim Ghosheh, were taken into custody as they arrived at Amman's airport and were charged with engaging in illegal political activities, while the third, Mousa Abu Marzook, was deported, officials said.

Jordan had threatened to arrest the men if they returned to Amman, but the three officials ignored the warning. Hamas, which has used terrorist attacks to try to disrupt the peace process between Israel and the Palestinians, is expected to try to capitalize on the arrests to rally supporters against the Jordanian government.

Israeli Prime Minister Ehud Barak praised Jordan's King Abdullah for ordering the arrests, but a senior Israeli intelligence official predicted they could mark the beginning of a showdown between Islamic militants and the Jordanian monarchy.

Jordan had allowed Hamas to exist openly until late August, when security officials shut down many of its offices, arrested several of its leaders and issued arrest warrants for the three men detained today. The men were in Iran at the time of the crackdown.

Israeli security officials maintain that the military wing of Hamas uses Jordan as its principal base for operations against Israel. Most members of the Hamas leadership are Palestinians who settled in Jordan following the creation of Israel in 1948.

U.S., Israeli and Palestinian officials had pressured Jordan to move against the group, saying that terrorism threatened to disrupt the recently renewed peace negotiations.

On Tuesday, Palestinian officials and senior Israeli intelligence officers said Hamas had expanded beyond the West Bank and Gaza Strip and established a network among Arab citizens of Israel to carry out terror attacks.

Riot police and soldiers backed by armored vehicles cordoned off parts of the Amman airport to prevent demonstrations by Hamas supporters when Meshal, Abu Marzook and Ghosheh arrived this morning on a flight from Iran, which also vehemently opposes peace deals with Israel.

Police arrested the three men as soon as they left the plane. Also detained were four bodyguards of Meshal, one of the most senior officials in Hamas, according to news reports. Meshal and Ghosheh, who are Jordanian citizens, were charged with affiliation with an illegal organization, Jordan's prosecutor general, Col. Mahmmoud Obeidat, said, according to the Reuters news service. They face a one-year prison term if found guilty.

After a brief interrogation, Abu Marzook, who holds a Yemeni passport and a Palestinian travel document, was asked to leave the country. Deputy Prime Minister Ayman Majali said Abu Marzook decided to return to Iran, Reuters reported.

The return of the Hamas leaders had been expected for some time. Through intermediaries, they had been trying to negotiate the reestablishment of operations in Jordan.

"In jail they will be more dangerous than in exile. To their followers they will become martyrs," said Mahdi Abdul Hadi, a Palestinian academic, in a recent interview.

However, Asher Susser, a Jordanian expert at Tel Aviv University, said the monarchy is strong enough to withstand the pressure. "The fact that it took action against Hamas is an indication of the regime's self-assuredness," he said.