BOGOTA, COLOMBIA, MAY 26 -- Colombia's presidential election Sunday has come down to a choice between a front-runner who vows to continue the war against drug traffickers and candidates who favor negotiating with the cocaine barons to end the bloodshed.

About 8 million Colombians are expected to vote amid a surge in violence that officials say is sponsored by the Medellin cocaine cartel and aimed at forcing the suspension of elections and disrupting Colombia's long democratic tradition.

Three presidential candidates have been assassinated in the past nine months by terrorists suspected of ties to drug traffickers, and a rising wave of shootings and bombings has greatly limited the candidates' campaign activities.

Today, Gen. Miguel Gomez Padilla, director of the National Police, announced the arrest of six persons who he said were responsible for a recent rash of car bombings in the capital, and confiscated more than a ton of Ecuadoran-made dynamite, 30 electronic blasting caps and 150 feet of fuses in the northern sector of the capital.

"Those arrested have links to narco-terrorism. Of that we are sure," Gomez Padilla said at a press conference. "This was an important cell that was planning on carrying out a series of terrorist actions today and tomorrow."

A car bomb in Medellin, the nation's second-largest city, killed seven people Thursday and nine policemen were killed there in the past week. Smaller car bombs exploded Friday in Medellin and Bogota.

The military is on its highest state of alert, and 130,000 policemen and soldiers are executing "Plan Democracy" -- patrolling the streets of the main cities, setting up mobile roadblocks, conducting random searches and arresting anyone deemed suspicious. Authorities in Medellin declared a 10 p.m. to 4 a.m. curfew and banned use of motorcycles -- regarded as the favorite transportation of cartel hit men -- and the sale of alcohol.

Liberal Party candidate Cesar Gaviria Trujillo, a 43-year-old economist and former cabinet minister, holds a commanding lead in most polls. He has vowed to step up the war against the drug barons and favors continuing extradition of suspected drug traffickers to the United States.

Gaviria, polling about 52 percent in recent surveys, argues that no deal can be reached with the traffickers because "we are dealing with the future of our country as a democracy. We are talking about the future of our children."

The Liberals, the majority party in Colombia for the past 50 years, are united around Gaviria, who entered the campaign following the assassination of Liberal candidate Luis Carlos Galan. Gaviria was Galan's campaign manager.

In contrast, the opposition Social Conservative party is deeply divided. Alvaro Gomez, 71, who was defeated as the party's candidate in 1985, is running as an independent and appears to be taking much of the party with him. Gomez, who favors legalization of cocaine by consuming nations to cut the cartels' profits, is running second in the polls with about 20 percent.

The Social Conservatives' official candidate, Rodrigo Lloreda, has centered his campaign on halting extradition in return for the traffickers' surrender and withdrawal from the drug business. He is polling about 18 percent.

Antonio Navarro Wolf, a former guerrilla commander of the M-19 rebels, is running fourth, with about 8 percent. His group reached a peace agreement with the government in March, and Navarro entered the campaign following the last month's assassination of M-19 candidate Carlos Pizarro.

Three of the candidates have crossed paths before. In 1988, Gomez was kidnapped by the M-19 guerrilla group, of which Navarro was a top commander, and held for several months. Gaviria, who was minister of interior, was responsible for the government's efforts to negotiate his release.