Colombian authorities have confiscated eight tonnes of cocaine along the border with Panama in what its president described as the "biggest seizure of drugs in history".

An estimated $240m worth of cocaine was seized on a banana plantation in the municipality of Turbo in Antioquia region by 50 commandos backed by helicopters, the national police agency said on Sunday.

Three people were arrested in the operation on the plantation where 359 canvas sacks loaded with packs of cocaine were hidden in a small cubicle under a cement cover 2.5 metres underground.

Three other suspects escaped, according to a police statement.

Defence Minister Luis Carlos Villegas said the drugs belonged to the Clan Usuga crime gang. The United States has offered a $5m reward for the capture of its leader.

Colombian President Juan Manuel Santos congratulated the police officials on Twitter, adding: "The operation in Turbo seized the largest amount in our history ... A crushing blow to the criminals".

Colombia produces about 442 tonnes of cocaine annually, according to the United Nations.

Last year, authorities seized 252 tonnes of the narcotic.

Authorities say the Usuga Clan, which emerged after the mass demobilisation of right-wing paramilitaries a decade ago, ships tonnes of cocaine from Colombia to Central America and on to the US.

Seizures of that size are rare but not unprecedented on a global scale. In March 2007, the US Coast Guard seized nearly 20 tonnes of cocaine found on a cargo ship - the Gatun - headed from the Panama Canal to the Mexican port of Topolobampo.

In 2001, the Coast Guard found 13 tonnes of cocaine aboard a Belize-flagged fishing boat that aroused suspicion while off the Mexican coast because it had no working fishing equipment and few fish.

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Source: Agencies