A militant Islamic cleric was arrested today for his alleged involvement in a series of church bombings two years ago by a radical network that intelligence officials have linked to al Qaeda, police said.

Abubakar Baasyir, who was hospitalized Friday in central Java after complaining of heart and respiratory problems, remained there while police tried to determine whether he was well enough to be taken to Jakarta for questioning.

Although police have not named Baasyir as a suspect in the deadly bombing in Bali a week ago, Indonesian Defense Minister Matori Abdul Djalil said that Baasyir would have had advance knowledge of the attack because of the suspected role of his deputy. Djalil said intelligence agencies had determined that Riduan Isamuddin, also known as Hambali, was Baasyir's chief lieutenant and a leading operative in al Qaeda-related terrorism in Indonesia.

"Al Qaeda and its internal network is behind this Bali bomb blast," Djalil said at a news conference in Bali. "It is illogical if Abubakar Baasyir says that he doesn't know about the bombings in Indonesia."

Baasyir's arrest comes one day after the government of Megawati Sukarnoputri, riding a wave of outrage over the Bali attack, which killed at least 183 people, issued emergency measures by decree that make it easier to detain people suspected of terrorist activities.

U.S. and Asian intelligence officials say that Baasyir, 64, heads Jemaah Islamiah, a radical Islamic network accused of plotting terrorist attacks in several Southeast Asian countries.

Baasyir has repeatedly denied involvement in terrorism and has said that Jemaah Islamiah does not exist.

The intelligence agencies have named Isamuddin as the primary link between Jemaah Islamiah and al Qaeda. He is now the most-wanted man in Southeast Asia.

While Malaysia and Singapore have sought Baasyir's arrest, he had lived freely in Indonesia until this week.

A team of Indonesian investigators this week questioned Omar al-Farouq, a suspected al Qaeda operative who was captured in June and is in U.S. custody at an undisclosed location. Farouq has reportedly told U.S. interrogators that Baasyir played a direct role in several terrorist attacks, including a series of church bombings in Jakarta and nine other Indonesian cities on Christmas Eve 2000. Nineteen people were killed and dozens injured in those attacks.

U.S. officials said Farouq repeated that account to the Indonesian investigators. After they returned to Jakarta, Indonesian officials said they had grounds to arrest Baasyir.

Police initially summoned Baasyir on Thursday to appear for questioning in Jakarta today. After attending Friday worship, during which he prayed for Osama bin Laden and later held a news conference, Baasyir was taken to a hospital in the central Java city of Solo.

National police spokesman Saleh Saaf suggested that Baasyir was faking his illness. "He's probably just pretending," Saaf told reporters this evening. "He was able to conduct a press conference in Solo. But right after we announced that his warrant had officially been issued, then he suddenly got sick."

The decision to arrest Baasyir came as the United States put intense pressure on Megawati's government to move against Islamic militants, including the cleric.

The Bush administration has already determined that there is sufficient evidence to designate Jemaah Islamiah as a foreign terrorist organization, but has held off to give the Indonesian government time to take its own action against the group, U.S. officials said. The United States and some Southeast Asian countries are moving toward asking the United Nations to name Jemaah Islamiah as a terrorist group, an action that could take place this week. The designation would impose financial and other sanctions against the organization and its members.

Indonesian officials said they expected the arrest to be unpopular with some radical Muslims. About 300 people, including students from an Islamic boarding school founded by Baasyir, protested today outside the hospital but dispersed without incident.

Family members visit radical Muslim cleric Abubakar Baasyir in his hospital room in central Java. Police want to take him to Jakarta for questioning.