Police have seized 10.8 tonnes of cocaine from Colombia's top crime gang, the biggest haul ever in the nation's long-running fight against drug trafficking.

The cocaine — with a US market value estimated by Santos at about of $US360 million ($470 million) — was found stored underground on four farms in a banana-growing region of north-west Antioquia province near Colombia's border with Panama.

"Thanks to a police operation with overseas intelligence, from friendly countries, the largest seizure in history was made," President Juan Manuel Santos said at a police base where the cocaine was laid out in packages on display.

He linked the cocaine to the drug-trafficking gang known as the Gulf Clan, which has become one of the biggest threats to security since peace was signed last year with Marxist-led Revolutionary Armed Forces of Colombia (FARC) guerrillas.

The seizure comes as the United States, Colombia's staunchest ally in the fight against drug trafficking, has raised concern over an increase in coca cultivation and as the government faces criticism from opposition politicians for allowing new crime gangs to fill the void left by the FARC.

Colombian police and soldiers stand guard over seized cocaine in Apartado. ( Reuters: Colombian Presidency )

Mr Santos, who leaves office next year, has pledged to send 80,000 military and police to areas once controlled by the FARC in a bid to prevent new trafficking gangs from taking hold.

Four people were arrested during the three-day operation leading to the drug seizure, according to a police statement.

The Gulf Clan is led by fugitive Dairo Antonio Usuga, known as Otoniel — the United States has offered a reward of up to $US5 million ($6.5 million) for information leading to his capture or death.

In addition to drugs, the gang deals in illegal mining and most if its estimated 1,500 members formerly served in the ranks of right-wing paramilitary groups.

Colombia is one of the world's leading producers of cocaine, with output of around 825 tonnes per year, according to the US Drug Enforcement Administration (DEA) — anti-drug police have confiscated 328 tonnes of cocaine this year.

Reuters