Suspected suicide bombers target Jakarta hotels; at least 6 victims, 2 bombers killed

JAKARTA, Indonesia (CNN) - Indonesian authorities believe two suicide bombers checked into the JW Marriott Hotel in Jakarta and carried out coordinated bombings Friday morning, killing at least six victims and wounding more than 50 others.

It is unclear what group is behind the attack on the Marriott and the adjacent Ritz-Carlton hotel, Indonesia's National Police Chief Gen. Bambang Hendarso said at a news conference. He warned that the death toll could rise. In addition to their victims, the two bombers also died in the attacks.

Indonesian authorities have detained several witnesses and others for questioning, and have sent forensic evidence from the scene for testing, a spokesman for Indonesian President Susilo Bambang Yudhoyono said.

"It's all being studied now," Dino Patti Djalal told CNN.

Yudhoyono warned that it is still too early to determine who was behind the attacks.

"This terrorist action is thought to be the work of a terrorist group, even though it is not certain whether this is the terrorism which we are familiar with up until now," the recently reelected president said.

The bombings at the two luxury hotels - which are connected by an underground tunnel - happened shortly before 8 a.m. (9 p.m. Thursday ET), first at the Marriott and then 10 minutes later at the Ritz-Carlton, police officials said. Five were killed at the Ritz-Carlton, and the other victim was killed at the Marriott, police spokesman Inspector General Nanan Soekarna said. A suspected suicide bomber died at each hotel as well, he said.

The hotels are frequented by international visitors and many foreign nationals are among those injured, including several American and Australian citizens.

An unexploded bomb was found on the Marriott Hotel's 18th floor where several suspects believed to be linked to the bombings were staying, Hendarso said.

It is unclear how they got around the "robust security" at the JW Marriott and the adjacent Ritz-Carlton Hotel, according to Allen Orlob, security chief for Marriott Hotels.