Juan Manuel Santos, the new president, who was sworn in on Saturday, visited the scene and urged Colombians to go on with their normal lives.

"As in every act of terrorism the aim is to generate fear," he said.

"We are going to continue fighting terrorism with everything we have."

Bogota's health secretary said most of the injured had been released after being treated for cuts, but three people remained under care. Most of those hurt had been on a bus that was passing by as the bomb exploded.

Critical radio station

Al Jazeera's Teresa Bo, reporting from the scene, said the last time a major blast occurred in Bogota was in 2003, when more than 30 people were killed.

"Things in Colombia have changed since then. Security is much better in this country now, but of course this is another proof that there is still a conflict going on, " she said.

"Caracol radio station has been criticising left-wing guerrillas, even left-wing President Hugo Chavez [of Venezuela], but also drug trafficking organisations and paramilitary groups.

"So for what we know right now anybody could have been behind this attack."

General Cesar Pinzon, Bogota's police chief, suggested the bomb could have been planted by the Revolutionary Armed Forces of Colombia (Farc) guerrillas that have been fighting the government for decades.

He said officials were not yet sure if the radio station was the target or several nearby bank headquarters.

The main anchorman of Caracol, one of the country's major radio stations, has received threats from armed groups before and has in the past left Colombia for his safety.

Caracol Radio continued broadcasting despite the blast.

Bombings and attacks on Colombian cities have dropped sharply since Alvaro Uribe, the former president, took office in 2002.

Violence has ebbed as Uribe's security campaign, with Santos in a key position as defence minister from 2006 to 2009, battered the Farc and drug traffickers.