Bombs shake Colombian capital

Colombia has been hit by a string of bombings

At least four people have been killed and about 20 injured in the Colombian capital, Bogota, by two bomb explosions.

First, a bomb exploded, and then we heard another explosion, and ambulances began arriving soon after

Witness

Two of the bombs went off during the morning rush hour near the campus of the National University. Bomb squads successfully deactivated a third device a short time later.

The area was later sealed off as police searched for further devices.

"First, a bomb exploded, and then we heard another explosion, and ambulances began arriving soon after," the Associated Press news agency quoted Elizabeth Martinez, a local resident, as saying.

Nobody has yet admitted responsibility for the blasts.

Bombing campaign

The bombs are the latest in a series of explosions in Colombia in recent weeks which have revived memories of a deadly bombing campaign carried out in the early 1990s by the former head of the Medellin drug cartel, Pablo Escobar.

Colombia is no stranger to violence

On Thursday, Colombian police deactivated two car bombs in the oil refining city of Barrancaberme, 230km (155 miles) north of Bogota.

One bomb was found in a taxi parked near a school and another in a car parked next to a bridge.

Earlier this week, police found a car bomb outside the offices of a communist magazine in Bogota. The bomb was reportedly big enough to wipe out a whole block of the city.

Another car bomb exploded last week in a fashionable district of Medellin, killing eight people and injuring 130.

Civil war

It went off next to a park lined with discos, bars and restaurants popular with business people and students.

The blasts are signs that Colombia's 37-year civil war may be spreading from the countryside to the big cities.

About 35,000 civilians have died over the last decade in the conflict, which pits left-wing guerrilla groups against right-wing paramilitaries and security forces.

Peace talks began two years ago between the largest rebel group, the Revolutionary Armed Forces of Colombia (Farc), and the government, but were broken off two months ago by the guerrillas. The conflict has since intensified.