BOGOTA, Colombia (AP) _ Soldiers in northern Colombia killed five members of a paramilitary squad reportedly run by drug traffickers, and police today said more than 500 people were arrested for violating a curfew in Medellin.

American dependents of U.S. Embassy employees were advised by the State Department to leave the country.

Also in Medellin, a rocket hit a paint factory early today, setting it on fire and injuring an undetermined number of people, radio station RCN reported. No one immediately claimed responsibility for the attack.

The 10 p.m.-to-6 a.m. curfew was imposed in Medellin and eight other cities as part of a nationwide crackdown on cocaine traffickers who have waged a campaign of assassinations, bombings and arson in recent weeks.

Medellin is considered the headquarters of the cartels that supply 80 percent of the cocaine to the United States.

National police said in a communique that 530 people were arrested for vioalting the first day of the curfew. All but two had been released by this morning, a police spokesman in Medellin told The Associated Press.

Meanwhile, a paramilitary band believed affiliated with drug traffickers clashed with an army patrol in a remote area of the northern state of Cesar, the Colombian radio chain RCN quoted military sources as saying.

Five of the attackers were killed, RCN quoted the army sources as saying.

Leftist guerrillas seeking to topple the government have generally been inactive during the recent war with drug lords, but new political violence broke out on Wednesday.

Six insurgents of the National Liberation Army were killed and one soldier was wounded in a battle Wednesday in the state of Cesar, the Bogota morning daily El Tiempo said.

Two policemen also were killed in a guerrilla ambush in the northeast state of Arauca, El Tiempo said, quoting police in Arauca.

Meanwhile, 12 bodies were found in a shallow grave in the state of Cordoba, El Tiempo said. One of the victims reportedly was identified as a veterinarian kidnapped several months ago by leftist rebels.

Leftist guerrillas also executed 10 of their own ranks, apparently for suspicion of being traitors, El Tiempo said, quoting sources with the army's 2nd Division in the northern state of Sucre.

In Medellin, a police force of 4,000 was on full alert and 18 special anti- terrorist units were stationed throughout the city.

''Everything has started with no major inconveniencies. People rushed to their homes shortly before the curfew time began and now the city is quiet,'' a spokesman at the Medellin Police Office said by telephone Wednesday night.

He said a fragmentation grenade exploded in a country club but caused only minor damage.

Interior Minister Orlando Vasquez Velazquez said the government would extend the curfew, the first in Colombia in 19 years, ''wherever it is required to prevent terrorism.''

He said Medellin, a city of 2 million, had ''become a center of perturbation.''

The U.S. Embassy gave no reason for ordering the dependents of its staff to leave, but it was clearly related to the Colombian campaign against drug traffickers and plans to extradite some suspects to the United States.

The extradition of one suspect, reputed Medellin cartel finance chief Eduardo Martinez Romero, was considered imminent.

An embassy spokesman, Peter Samson, said in a telephone interview: ''U.S. Embassy dependents have been ordered to leave Colombia in the next few days. That's all I can tell you.''

Because of the recurring violence in Colombia, the embassy already had a policy of not allowing dependents under the age of 18 but had permitted older children, spouses, parents and other adult dependents. The embassy order would apply to up to 50 relatives of Embassy staffers, a source said.

The order also recommended that U.S. students leave Colombia. The U.S. State Department last week urged American tourists to stay away from Medellin to avoid the possibility of getting caught up in the violence there.

The city has suffered almost daily bombing attacks by drug traffickers, who are pressing the government to end its 13-day-old crackdown and negotiate a peace. The government began its offensive after a string of assassinations that culminated Aug. 18 with the slaying of Sen. Luis Carlos Galan, the leading presidential hopeful.

Authorities since have arrested several mid-level drug dealers in raids in which they seized more than $200 million in property, including lavish estates, office buildings, airplanes and cars allegedly obtained with drug money.

The drug barons responded by declaring war on the government.

Medellin and surrounding communities have been rocked by at least 18 bombings and three arson attacks, according to police reports. Several other bombs were found and deactivated.

In Washington, an administration source said Wednesday that when President Bush presents his drug control strategy next week, he will call for up to $260 million in economic and military aid for the three principal cocaine-producing countries - Colombia, Peru and Bolivia.