Environmental campaigners in Colombia have boarded a ship carrying genetically-modified (GM) corn from the United States.

Greenpeace said five of its members used power boats to reach the cargo ship shortly before it docked at the Caribbean port of Santa Marta.

They were later arrested.

The incident coincided with an international conference on genetically modified products in the nearby city of Cartagena.

Representatives from more than one-hundred-and-thirty nations are meeting to debate how to regulate trade in genetically-modified crops.

So far they've failed to reach an agreement. Environmental groups and many developing countries consider the proposed pact too flexible and insist on legal guarantees to protect them against any environmental damage and threats to traditional crops.