A car bomb detonated outside a police station in southwestern Colombia on Thursday, killing six people and wounding 30 in the region's second such attack in less than 48 hours, officials said.

Those killed in the blast in the town of Villa Rica, in the department of Cauca, included the police station commander and at least three civilians, said Mayor Juan Guillermo Mina.

The station was nearly destroyed along with several nearby shops, television news footage showed. "We have never had this type of incident occur here and I hope that it never happens again," Mina said.

The bombing came one day after nine people were killed and 69 wounded when the police station was bombed in the far southwestern port town of Tumaco. It was the third bombing in Tumaco this year, local officials said.

The government blamed leftist rebels with the Revolutionary Armed Forces of Colombia (FARC) for the Tumaco attack. While the Thursday attackers were unidentified, military officials say a FARC front operates in the region.

Colombian President Juan Manuel Santos, who traveled to Tumaco, said Thursday he was increasing security forces in the region.

"There is no justification for the attacks, and what they are doing is making any possibility of peace more difficult," said Santos.

He said Tumaco has suffered enormously because it is a "strategic center for narcoterrorism," and announced he would be sending 2,500 soldiers and marines, as well as 300 police officers, to the city.

Defense Minister Juan Carlos Pinzon said the Tumaco attack was carried out by FARC guerrillas in alliance with Los Rastrajos, a criminal gang made up of former drug traffickers and ex right-wing paramilitary fighters.

The FARC, founded in 1964, has an estimated 8,000 fighters across Colombia, according to the Ministry of Defense.

Leftist guerrillas with a rival group, the National Liberation Army (ELN), are also active in southwestern Colombia.

The various groups are struggling to control regions of Colombia's Pacific coastline, key for exporting illegal drugs and smuggling in weapons.