Two homemade bombs exploded simultaneously at dawn inside two hotels and a third went off later outside another hotel at Basilan's busy business district near Zamboanga port city in southern Philippines, police and military said.

The first explosion occurred on the second and third floors of the Paradise Hotel at 3.30 am.

Another ripped through the third floor of the Imperial Hotel several minutes later. The blast shattered windows of a nearby small building.

A third bomb, placed inside a black bag, was left hanging at an electrical post near the Platinum Hotel. It was discovered at around 4:45 am by a security guard who informed the police.

The watchman placed the bomb on the street, but it exploded later before police and military explosives experts could disarm the bomb, a radio station said.

"No one was hurt in the blast. There were no major damages," said the commander of an elite military anti-terrorist task force Army Col. Alexander Yano.

No group claimed responsibility in the attack.

Our Manila Bureau Chief adds: Fifty were reported killed in the ongoing clash between government soldiers and the Abu Sayyaf in Lantawan town, Basilan which began on Sunday, Southern Command Chief Lt. Gen. Roy Cimatu said in a phone interview.

The group is believed to belong to Abu Sayyaf leader Khadafy Janjalani, said Cimatu.

A total of 39 rebels and soldiers were wounded during the second day of the encounter, Cimatu added. Also wounded was rebel sub-leader Isnilon Hapilon, Cimatu said.

At the same time, Armed Forces Chief Gen. Diomedio Villanueva called for the safe rescue of the two American and 16 Filipino hostages.

"The safety of the hostages have been properly taken cared of. We have given that instructions to our troops," said Villanueva.

Later, the military halted its rescue and offensive mission due to heavy rains. "Our operations were limited to ground movements. We have been trained for this," said Cimatu, adding: "The battlefield is a large coconut plantation."