MANILA, Philippines (AP) _ Five explosions rocked Manila on Saturday, killing at least 11 people and wounding more than 90 others as they ripped apart a bus and a train coach and hit an airport, a gas station and a park.

Edgardo Aglipay, the police chief for metropolitan Manila, said police suspected the attacks were the work of extremist Muslim rebels. They came a day after all Manila-area police were put on alert for Christmas-season bombing attacks by the Abu Sayyaf rebel group.

The first four blasts occurred nearly simultaneously around midday Saturday. Police later found a fifth bomb at a gas station near the posh Dusit hotel and tried to defuse it, but it exploded as they worked, killing one bomb expert and wounding another.

The blast on the train appeared to have been the most destructive: The light railway transport train's front coach was blown apart as it pulled into Manila's Blumentritt Station at noon. At least nine people died and more than 60 were hurt. Shattered holiday gifts and lunch baskets were strewn for yards around at the busy station.

``The train was approaching when I heard the explosion in the front coach,'' said Mari Vicpaglan, a ticket clerk at the railway station. ``It was so loud. I tried to help them. I felt dizzy because of the number of people pleading for help.''

Police said they didn't yet know who was responsible for the train blast. They said they had taken one witness in for questioning but would not say if the person was a suspect.

Elsewhere, a bomb exploded in a bus inside the main bus terminal in Quezon city, in the greater Manila area. At least one person died, 15 were hurt and the terminal was severely damaged.

A third blast came near a large aviation fuel depot at Manila's Ninoy Aquino International Airport. At least three people were hurt, said an airport official, but the fuel depot did not explode.

The fourth bomb exploded on a bench in a park near the U.S. Embassy, wounding at least nine, blasting a two-foot crater in the ground and damaging buildings some 200 yards from the embassy. The bomb apparently was not directed at the embassy itself.

Lonnie Kelley, acting spokeswoman at the U.S. Embassy, said the embassy was not damaged and she knew of no injured staff members.

``Normal security procedures are taking place,'' she said. ``Security has been heightened in the past and we're not taking any extraordinary measure now.''

The attacks left many Manila residents nervous and police swamped with reports of suspicious packages. Several commercial centers were evacuated after false alarms.

Witnesses said a suspicious package on a counter in a shopping mall sparked a stampede as people fled the building. Police bomb experts found dried fish and mangoes in the package.

The areas hit by the explosions were cordoned off, holding back masses of onlookers, and television stations were calling on people to stay away from the blast scenes. President Joseph Estrada called an emergency Cabinet meeting and was to speak about the attacks later. A statement from the presidential palace appealed for calm and said police will guard public areas, particularly transportation centers.

The Philippines has long grappled with a multitude of religious and political conflicts as well as rising crime. In the south, two Muslim separatist guerrilla groups have been fighting for a separate Islamic nation. The larger group, the Moro Islamic Liberation Front, has been blamed for bombings in Manila in the past.

The smaller but more radical of the two groups is called the Abu Sayyaf. Manila police recently warned that Abu Sayyaf members were planning bomb attacks in the city during the Christmas holidays.

On Thursday, police arrested Abu Sayyaf spokesman Hector Janjalani in Manila. They said he had several grenades and sketches of potential targets in the city.

Earlier this year, Abu Sayyaf rebels abducted scores of foreigners and Filipinos in the country's worst hostage crisis.

All but two of the hostages, an American and a Filipino, were freed in exchange for huge ransoms, officials said. The military began a massive offensive against the guerrillas on southern Jolo Island on Sept. 16 to rescue the two captives and neutralize the rebel group.

Saturday's attacks came as Filipinos were grappling with political instability caused by a presidential impeachment trial.

Estrada, a former action-film star, is being tried in the Senate on charges of bribery, graft, betrayal of public trust and violating the constitution. The trial began this month and is to continue after a holiday recess.