Indonesian police have arrested a man they said organized the massive bombing in Bali two months ago, recording the latest breakthrough in a fast-moving investigation.

Police announced today they had captured an Indonesian cleric named Mukhlas, described by Asian intelligence officials as the operational chief for the regional Jemaah Islamiah network, during a raid late Tuesday in central Java.

The arrest came as a welcome surprise to terrorism experts, because they had repeatedly speculated that Mukhlas was hiding in Malaysia, where he had taken over operational responsibilities for Jemaah Islamiah from another Indonesian militant, Hambali.

Western and Asian security officials have identified Hambali, whose real name is Riduan Isamuddin, as the network's main liaison to al Qaeda, making him the most-wanted man in Southeast Asia. But officials in Singapore and elsewhere in the region said in recent weeks that Hambali had turned over his responsibilities after he became the object of a global manhunt.

Muchyar Yara, spokesman for Indonesia's national intelligence agency, said he was confident that investigators would be able to follow the fresh trail to the top of the region's radical network. "I hope we'll be able to get to the big guy soon, Hambali," Yara said.

He added that the recent progress could also help strengthen the case against another Islamic cleric, Abubakar Baasyir, who has been named by the United States and other governments as the leader of Jemaah Islamiah. "The sooner we get the soldiers, the sooner we get to the general," Yara said, explaining that he meant Baasyir. Baasyir was arrested by Indonesian police two months ago for alleged involvement in a series of church bombings on Christmas Eve 2000 and a plot to assassinate President Megawati Sukarnoputri. So far, investigators have not linked him directly to the Oct. 12 attack in Bali, which killed about 190 people.

Indonesian police investigating the bombing of Bali's teeming nightclub district arrested Mukhlas in the town of Klaten along with eight other people, including his wife, according to Gen. Erwin Mappaseng, national police chief for criminal investigations. Authorities discovered a handgun, bullets and radical Islamic literature during the sweep, he said.

Mukhlas's capture came after police last month arrested his younger brother, a mechanic named Amrozi, who told authorities that he was the owner of a minivan used in the attack.

Amrozi's confession helped lead investigators to the plot's alleged field commander, Imam Samudra, caught two weeks ago as he was preparing to board a ferry from Java to the neighboring island of Sumatra. Indonesian security officials said they believed Samudra received his orders from Mukhlas.

According to investigators, Mukhlas lived for the last decade outside Indonesia, primarily in Malaysia, where he ran a radical Islamic school in the southern state of Johor. Several Indonesian militants, including Baasyir, taught at the school.

Mukhlas, also known as Ali Ghufron, is a veteran of combat in Afghanistan, and fought U.S.-led forces after Sept. 11, 2001, Asian security officials said. Earlier this year, officials in Singapore said he was also involved in a plot to blow up pipelines that carry water from Malaysia to Singapore. The attack was never carried out.

The capture of Mukhlas is "a major coup for the people who arrested him," said Sidney Jones, Indonesian director for the International Crisis Group and an expert on radical Islam in Indonesia, the world's most populous Muslim country. "Potentially, if he does talk, we'll know much more about the structure of Jemaah Islamiah. It could be a devastating blow to the Jemaah Islamiah organization."

Rohan Gunaratna, a Southeast Asia terrorism expert, said the leads gathered by Indonesia could ultimately lead beyond Hambali to Khalid Sheik Mohammed, who heads al Qaeda's military committee. It was Mohammed who directed Southeast Asian militants to consider shifting tactics this year and begin striking "soft" targets such as bars and nightclubs, Gunaratna said. During discussions in southern Thailand and Bangkok, Mukhlas and Hambali first talked about targeting Bali, according to Gunaratna, author of "Inside al Qaeda."

Another regional security analyst said Mukhlas is a valuable prize because he was responsible for networking among militant cells.

As the Bali probe has made swift progress, Indonesians and foreign officials alike have praised the role of Maj. Gen. I Made Pastika, the police chief who leads the international investigation. These officials note that Pastika remains committed to the probe, even if the trail should lead to prominent Islamic clerics such as Baasyir. Others in the government have been reluctant to pursue such an aggressive course, fearing this could provoke a backlash among some Muslims.

Indonesian police officers arrested Mukhlas in central Java on Tuesday.