At least 20 people are now known to have been killed when a powerful explosion ripped through an exclusive club in the Colombian capital, Bogota.

Investigators say the blast was caused by explosives - possibly a car bomb placed in an indoor car park at the Club Nogal, which is frequented by Colombia's political elite and foreign diplomats.

It was a huge explosion - I thought an airplane had crashed outside Luis Moreno witness

More than 110 people were injured in the blast, which blew the facade off the 10-storey building scattering debris over Seventh Avenue, the city's main street, which was crowded at the time with revellers or people heading home.

Firefighters are working to reach survivors believed to be trapped on the sixth to eight floors and to put out the blaze.

"It was a huge explosion - I thought an airplane had crashed outside," Luis Moreno, who lives across the street from the club, said.

Colombian TV said the blast had occurred on the third floor at 2015 (0115 GMT) and had torn a hole through the building which was "quite full" at the time.

Media reports said there were many children in the building at the time of the blast.

President Alvaro Uribe has visited the scene of the explosion.

Rebels suspected

The explosion came just hours after national police head General Teodoro Campo announced that his officers had thwarted a string of planned city bombings.

Incidents such as this have occurred regularly in Bogota in recent years and are usually blamed by the government on left-wing rebels.

Fingers are pointing at the country's largest rebel group, the Revolutionary Armed Forces of Colombia (FARC), the BBC's Jeremy McDermott reports.

The group has, our correspondent says, brought its 39-year war against the state into the cities with a wave of car bombs and attacks with mortars on government buildings.

'Fireball'

As black smoke poured from the building and flames licked around the upper windows, paramedics treated the injured in the rubble.

One witness, Catalina Ortiz, said she was passing the scene in a car with her daughter and husband when she thought the vehicle had been hit.

CLUB NOGAL

Advertises itself as "one of the most important corporate, social and cultural centres in Bogota" Features children's and young people's areas - they were due to close just minutes before the blast Other facilities include: five eating areas, an art gallery and 10th-floor swimming-pool

"When I looked back, I saw the club was on fire, with a ball of fire coming out of the third or fourth floor," she said.

"While I was looking back, things began to fall out of the building."

The club features luxurious meeting rooms, a squash court, swimming pool, sauna, hotel and several restaurants.

Bogota Mayor Antanus Mockus said a theory that the explosion may have been an accident had been discarded by investigators.

Colombian media are pointing to a bomb in a car parked on the third floor of the club's parking lot.