Colombia's President Juan Manuel Santos has announced a 500 million peso ($277,000) reward for information leading to those responsible for a deadly bomb attack which targeted a former interior minister.

The midday bombing on Tuesday killed two bodyguards of Fernando Londono and injured at least 39 people in a
busy commercial district of Bogota, raising fears that violence not seen in the Colombian capital in years could return.

Londono, 68, had glass shards removed from his chest and was out of danger, authorities said.

But his driver and another bodyguard were killed almost instantly. Gustavo Petro, Bogota mayor, said a pedestrian attached an explosive to Londono's armoured 4WD vehicle and set it off remotely.

Colombia has battled leftist guerrillas, right-wing paramilitary groups and drug cartels for decades. However, a campaign since 2002 against cocaine traffickers and rebels coupled with the demobilisation of paramilitaries has sharply reduced violence in Bogota.

Long black hair

Authorities said they had video of Tuesday's attack and Petro said the culprit "walked away disguised". A wig of long black hair and a hat were found nearby.

"We condemn this attack ... this government will not be thrown off course by these terrorist attacks. We will stay the course and carry out all the investigations needed to find the culprits," Santos said after the attack.

Speculation was widespread that the country's main leftist rebel group, the Revolutionary Armed Forces of Colombia, or FARC, was to blame. But Santos said it was too early to assign blame.

"We don't know who is behind this attack," he said after meeting with police and military brass, Petro and the chief prosecutor.

The FARC was behind a car bomb, however, that was detected and de-activated elsewhere in Bogota earlier on Tuesday, Santos said.

Largest and boldest

Lucia Newman, Al Jazeera's Latin America editor, said on Tuesday that Bogota has not seen attacks on this scale for years.

"Although there have been smaller bombings in past years, and more recently in front of Radio Caracol in Bogota, this attack is seen as the largest and boldest in many years," she said.

"The bomb was placed on top of the vehicle of Londono, who is a rightwing and conservative politician, who has a daily radio programme La Voz de la Verdad, or the Voice of Truth, as well as a newspaper column in El Tiempo.

"He uses both to fiercely attack the FARC and is a staunch supporter of ex-president Alvaro Uribe."

Local television broadcast images of him walking from the scene of the bomb attack with blood covering his face, flanked by a bodyguard carrying a gun.

Santos said Londono had in the past received death threats and had a sophisticated protection scheme involving about 19 bodyguards.

Source: Al Jazeera and agencies