A massive 12 tonnes of cocaine has been seized by police in Colombia - the biggest ever haul in the nation's long-running fight against drug trafficking.

The cocaine, valued at around $517 million [$US360 million], was stored underground on four farms in a banana-growing region, near the border with Panama.

Colombia's President Juan Manuel Santos 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 guerrillas.

Colombia is one of the world's leading producers of cocaine, with US officials saying it makes around 910 tonnes per year.

The news follows New Zealand's biggest ever haul two weeks ago, with $20 million worth of cocaine seized in Tauranga.