BOGOTA, COLOMBIA, OCT. 13 -- Violence spread through Colombia today as workers went on strike, the government closed schools and a political party tied to the country's largest guerrilla group buried its slain hero.

While 20,000 mourners accompanied the bullet-riddled body of Jaime Pardo Leal to the cemetery, reports of a guerrilla attack in Bucaramanga and violent confrontations between police and students in Barranquilla and other towns seemed to confirm fears that Pardo Leal's death has set back Colombia's hopes for domestic peace.

Eleven persons have been killed in political violence since Pardo Leal, 47, was shot down Sunday by unknown assassins in a town 30 miles south of here. As presidential candidate of the Patriotic Union, he had helped lead Colombia's largest guerrilla group out of the mountains and into the electoral process.

The party is tied to the left-wing Revolutionary Armed Forces of Colombia, and security forces were on alert for a retaliatory blow by the guerrillas.

Bogota, where the assassination of populist leader Jorge Gaitan in 1948 started a civil war, was tense.

As today's funeral procession for Pardo Leal passed through the narrow streets of the central business district, sporadic violence erupted between police and mourners. Some stragglers smashed the windows of about 50 stores and stripped them of merchandise. Police said two looters were shot and injured. Dozens of people were arrested.

During the past two days, protesters have erected barricades made of burning tires on main streets passing near Bogota sprawling slums.

Owners of bus lines locked up their vehicles in fear of armed attacks, and a 48-hour general strike called by the Unified Workers' Central, Colombia's main labor federation, emptied Bogota's streets and closed workplaces around the country.

Regional governments closed schools and imposed a ban on the sale of alcohol, and national leaders asked for calm.

Army troops were called out to patrol cities and towns.

A 13-year-old boy was shot and killed in the central Colombian town of Barrancabermeja and his father was wounded when soldiers tried to break through a roadblock of burning tires, the National Police said in a communique.

President Virgilio Barco has blamed Pardo Leal's death on "enemies of peace and democracy." The government has appointed a special prosecutor in the case. No suspects are in custody, but it is widely assumed that Pardo Leal was shot by killers working for opponents of plans to open the two-party system to a third contender for power.

Although Pardo Leal, an attorney identified with leftist causes, only received 4.4 percent of the ballots when he ran for president last year, his party put 18 candidates in Congress, establishing it as the most successful leftist party in Colombia's history. Of the 18 legislators four have since been killed.

The main problem that the party's candidates face is staying alive. In what is an apparent attempt to eradicate the electoral threat from the left, 471 members have been murdered, by the party's count, since it was founded in 1985.

The peace process begun three years ago by president Belisario Betancur persuaded Pardo Leal's guerrilla band to sign a cease-fire and launch the Patriotic Union, but the leader of the still extant rebel army, Jacobo Arenas, told journalists in August that his group would unite with other guerrilla groups and return to the armed struggle if the killing of the party's leaders did not stop.