JAKARTA, Indonesia — Suicide bombers who checked in as guests smuggled explosives into American luxury hotels in Indonesia's capital and set off a pair of heavy blasts that killed eight people and wounded more than 50, investigators said today.

The near-simultaneous bombings ended a four-year lull in terror attacks in the world's most populous Muslim nation. At least 18 foreigners were among the dead and wounded.

The blasts at the J.W. Marriott and Ritz-Carlton hotels, located side-by-side in an upscale business district in Jakarta, blew out windows and scattered debris and glass across the street, kicking up a thick plume of smoke. Facades of both hotels were reduced to twisted metal.

An Australian think tank, the Strategic Policy Institute, predicted the Southeast Asian terrorist group Jemaah Islamiyah might launch new attacks just a day before today's deadly strike.

A paper released Thursday said tensions in the group's leadership and the release of former members from prison "raise the possibility that splinter factions might now seek to re-energize the movement through violent attacks."

Indonesian President Susilo Bambang Yudhoyono said the attack was carried out by a "terrorist group" and vowed to arrest the perpetrators. He also suggested a possible link to the national election last week that is expected to hand him another five-year term as president, but he provided no details.