A car bomb in the regional capital of Cali killed four people and injured 26 outside the justice building overnight, and the provincial government offered a reward of 100 million pesos(US$55,000) on Monday for information leading to the capture of those responsible.

"The victims were left unidentifiable, burned and totally mutilated," Cali Mayor Jorge Ivan Ospina told The Associated Press in a telephone interview. "Whoever commited this criminal act, this act of terror against the heart of Cali, deserves justice."

The vehicle packed with about 80 kilos of explosives was set off at the stroke of midnight. The last time the city of two million suffered such an attack was in April 2007, when a car bomb killed one person outside a police station.

Ospina said it was too early to tell who was responsible, despite claims by some police officials that the leftist Revolutionary Armed Forces of Colombia were to blame. Defense minister Juan Manuel Santos said there were "clear indications" pointing FARC responsiblity, but did not offer details.

Valle del Cauca Gov. Juan Carlos Abadia, who announced the reward offer, said the bomb also damaged the first floor of the judicial building, where files containing evidence against criminals are held.