MANILA, AUG. 26 -- Police fired into a crowd of rock-throwing strikers today, wounding four seriously, as the first general strike against President Corazon Aquino's government crippled transportation and slowed work at factories and offices in several Philippine provinces.

About 5,000 demonstrators marched to the presidential palace in Manila to protest higher fuel prices, carrying signs that denounced Aquino as an "American puppet." The marches were blocked 500 yards from the palace gates by barbed wire barricades guarded by riot police and fire trucks.

The march ended peacefully, but strike leaders said about 120 protesters were arrested and others injured in clashes with police elsewhere in Manila and in Cebu City, the country's second largest city, 350 miles south of the capital. Strikes were also reported in the provincial cities of Davao, Iloilo and Bacolod.

A police spokesman said two policemen were injured by a homemade fragmentation bomb thrown by strikers in Bacoor, 10 miles south of Manila. Authorities reported that strikers stoned vehicles and youths barricaded streets in Manila and outlying cities.

The labor unrest erupted after the government announced a fuel price increase on Aug. 14. Following several days of sporadic protests and transport strikes, Aquino went on national television yesterday to announce a price rollback that effectively cut the increases in half and helped defuse what could have been much larger demonstrations.

Although leaders of the radical left-wing May 1st Movement failed in their bid to fill the streets with 2 million people, the strike succeeded in disrupting transportation and work in factories, as well as government and private offices. Officials reported that schools were closed, and most offices and factories operated at half-strength in the country's largest urban centers.

"We would like to remind President Aquino and her officials that unless they change their policies, they will, like {deposed president Ferdinand} Marcos, be driven out of government," said Crispin Beltran, leader of the May 1st Movement.

The strike was called as a show of rejection of Aquino's partial rollback. She told reporters today: "I tried to do my best. I will just have to appeal to our people to understand {the economic} predicament of the government."

One Filipino analyst described the strike as perhaps the most effective the political left had ever mounted. It was impossible, however, to gauge how many workers stayed off their jobs because of sympathy toward the strikers or out of fear of harassment and violence by strikers.

Analysts had viewed the strike as a key test of the left's strength following its crushing defeat in legislative elections three months ago. There was some speculation today among Manila commentators that the strike signaled a weakening of Aquino's support in the more moderate left and even among some of her centrist supporters.

The strike attracted more support than previous leftist-led protests because it involved a bread-and-butter issue. The question for the left is whether it can effectively exploit economic issues as a springboard to expand its urban protest movement aimed at weakening Aquino.

Protest leaders vowed to continue the strike until the Philippine president lowers fuel prices to previous levels.

The most serious violence was reported in Bacoor, where police said 1,000 demonstrators blocked a major intersection and refused to budge for several hours. After the protesters defied a police order to disperse, authorities sprayed the crowd with fire hoses and fired tear gas. The demonstrators responded with rocks.

Authorities said homemade fragmentation bombs were also hurled at police lines, injuring two policemen.

Strikers, however, disputed the police version. Emelita Salyoto, a demonstrator who suffered a gushot wound during the melee, told a television interviewer as she lay in the street waiting for an ambulance: "All of a sudden they {police} bombarded us with water hoses, then I heard gunshots."

In Manila, police used fire hoses and clubs to disperse several hundred strikers who were joined by Catholic priests, nuns and seminary students along a major boulevard. Earlier in the day, the strikers had blocked four lanes of the eight-lane thoroughfare, snarling traffic and harassing "jeepney" (or minibus) drivers who ignored the strike.