President Andres Pastrana flew to the northern port city of Cartagena to inspect the haul, which was discovered during a joint operation by the navy and secret police.

Once again we are dealing blows to the great financiers of violence in Colombia

President Andres Pastrana

Six people were arrested in Tuesday's raid on a farm at San Onofre, near the Gulf of Morrosquillo.

The cocaine, which was hidden in an underground cellar, is thought to have been destined for the United States and Europe.

US aid in drugs war

Mr Pastrana said the haul was almost equivalent in value to the amount Colombia was requesting in aid from the US to help fight drug-trafficking.

President Pastrana (left) inspects the packages

President Bill Clinton has strongly backed the aid package, but it has been held up by a spending row in the US Congress.

Colombia is thought to be the source of about 80% of the world's cocaine, and also a major source of heroin.

The cocaine bricks laid out at Mr Pastrana's feet represented 1% of Colombia's estimated annual 520-tonne production of the drug.

"Once again, we are dealing blows to the great financiers of violence in Colombia," Mr Pastrana said.

Paramilitary stronghold

The area around San Onofre, about 400km (240 miles) north of the capital Bogota, is a stronghold of right-wing death squads.

The latest drugs haul was the biggest since mid-February, when the authorities seized six tonnes of cocaine in a joint operation with the US Coast Guard aboard a vessel that had set sail from Colombia's Pacific coast.

The biggest ever cocaine seizure in Colombia took place in December 1998, when police in Cartagena discovered more than seven tonnes of the drug cocaine hidden in shipping containers.