Indonesian security forces were investigating unconfirmed reports that a homicide bomber was planning to infiltrate demonstrations during U.S. President George W. Bush's visit to the Muslim nation on Monday, police said.

Bush's whirlwind trip comes amid mounting anger over U.S. Middle East policy and the invasions of Iraq and Afghanistan — seen by many in Indonesia as attacks on their faith.

Islamic hard-liners and students vowed to disrupt the six-hour visit in the hilly town of Bogor, where Bush is scheduled to hold wide-ranging talks with President Susilo Bambang Yudhoyono.

Several thousand marched to the city's main mosque early Monday, some carrying posters showing victims of violence in the Iraq and Palestine as others unfurled a banner calling him a terrorist and war criminal.

Security was tight, with thousands of police and rifle-toting soldiers patrolling the streets near Bogor's presidential palace.

The city's police chief, Sukrawardi Dahlan, said his forces were investigating unconfirmed reports "that man wearing a (homicide) vest would infiltrate the (anti-Bush) protests" on Monday.

He was vague about the source of the information, citing only "media reports, local organizations and contacts," and refused to say if intelligence networks had confirmed reports of a plot.

But it was being taken seriously, Dahlan said.

"We're very sensitive about such reports ... because, in fact, we have had suicide bombers in Indonesia wearing jackets or backpacks," he said. "We want to protect the people."

Indonesia is a secular country, and most of its 190 million Muslims practice a moderate form of the faith, but the government is grappling with a rise in extremist thought.

The country has been hit by a string of terrorist attacks blamed on the Al Qaeda-linked militant group Jemaah Islamiyah since 2002, including two in Jakarta and two on the resort island of Bali together killed nearly 240 people.