A car bomb exploded in the Colombian port city of Buenaventura Wednesday killing at least nine people and wounding 50 others, according to media reports.
Officials in Valle del Cauca province initially confirmed three deaths and said 18 others were wounded, dpa reported.
According to media reports, others died while being treated for their wounds. Most of the injured suffered burns, broken bones or were hit by shrapnel.
The blast took place in central Buenaventura, a city of about 350,000 people and the country's main port on the Pacific coast. The bomb-laden car had been parked at the site on Tuesday evening.
The attack happened near the offices of the mayor and the attorney general. One public prosecutor, one assistant, two police officers and four investigators were reportedly injured in the blast, which caused great damage within a radius of several blocks.
The motive behind the bombing was not immediately clear. However, Colombia has been for over four decades the scene of an internal conflict, as leftist guerrillas including the Revolutionary Armed Forces of Colombia (FARC) and extreme-right paramilitaries fight each other and the central government for control.
While some officials blamed the attack on FARC, others believe drug traffickers to be responsible.
President Alvaro Uribe condemned the attack, but did not directly blame any group. "We cannot let our guard down," he said. "... this act shows we cannot allow ourselves to be too confident."
Former defence minister Juan Manuel Santos, the ruling party's presidential candidate, was due to visit the city Wednesday, and security measures had been increased.
Buenaventura, Colombia's main port on the Pacific Ocean, has been the site of several attacks in recent months, which the authorities have blamed on FARC and on drug traffickers.
On Tuesday, seven trucks were set on fire on a road into Buenaventura, in an attack that was also blamed on FARC.
Also on Tuesday, five kidnapped oil workers were rescued during a military offensive in eastern Colombia. The workers had been kidnapped on Saturday.
The operation took place as opposition Senator Piedad Cordoba said FARC had agreed to security arrangements for the release of two prisoners of war to the International Committee of the Red Cross by week's end.
The rebels said they would turn over Army Corporal Pablo Moncayo, in captivity since 1997, and a soldier captured in 2009.
Frank Pearl, the government's peace commissioner, said a ceasefire would go into effect Friday evening through Sunday morning to allow the prisoner release.
FARC announced in April 2009 that it would release the two prisoners, but disagreements over security arrangements with the government delayed it for nearly a year. About two dozen soldiers and police are currently being held captive by the rebels.