Indonesian police warned Saturday that the threat of an attack by Al Qaeda-linked militants has increased sharply ahead of U.S. President George W. Bush's visit to the world's most populous Muslim country.

Bush arrives Monday for talks with President Susilo Bambang Yudhoyono that will touch on the Middle East crisis and the U.S.-led invasions of Iraq and Afghanistan — the cause of mounting anger among Indonesia's 190 million Muslims.

Though most people here practice a moderate form of the faith, hard-liners are gaining ground and Jakarta's police chief, Maj. Gen. Adang Firman, told reporters that the threat of an attack by militants had "escalated sharply" in recent days.

He did not elaborate or say if a plot by the Southeast Asian militant group Jemaah Islamiyah had been uncovered.

The terror network has been blamed for a series of attacks targeting Western interests in Indonesia since 2002, including nightclub and restaurant bombings on the resort island of Bali and blasts at the Australian Embassy and the J.W. Marriott Hotel in the capital.

More than 240 people were killed, many of them foreign tourists.

Though Jemaah Islamiyah has been crippled by hundreds of arrests in recent years, one of its alleged leaders and most deadly operatives, Noordin Top, is still at large, so "we have to remain vigilant," said intelligence chief Syamsir Siregar.

Security will be tight on Monday, with more than 18,000 police deployed in the hilly city of Bogor, where Bush and Yudhoyono will meet.

Islamic groups and students have vowed to come out in full force to protest Bush's visit. They have held small but rowdy demonstrations in cities nationwide almost every day this week, including a rally Saturday in front of the U.S. Embassy in Jakarta.

"Bush is a terrorist!" chanted 300 protesters gathering beneath a blazing sun. "He is guilty of killing Muslims!"

Hundreds also turned out in Bogor, where rifle-toting soldiers, police and members of an elite anti-terror squad could be seen patrolling the streets near the presidential palace.

A bomb squad was briefly called in to investigate a suspicious vehicle left unattended for two days, but police towed the sedan away after explosives experts determined it posed no danger.

Protests also were held in the cities of Surabaya, Yogyakarta, Bandarlampung and Mataram, and on Bali.

Asked about the terrorism threat, Widodo Adisucipto, a government minister overseeing law and order, said extra "security precautions had been taken."

"There's no reason to panic," he said.

Last week, a man detonated a small bomb at an American fast food restaurant in Jakarta, but police have ruled out any links to Jemaah Islamiyah or Bush's visit, saying the attacker appeared to have been suffering from a psychological disorder.

Only the suspect was hurt in the blast.