The Colombian authorities say right-wing paramilitaries killed at least twenty-one people at the weekend in attacks on two villages in the north of the country.

Another fifteen people were abducted and are also reported to have been killed.

Witnesses said heavily armed men dragged people from their homes and shot them while other residents watched in horror.

Meanwhile, army officials say at least six left-wing guerrillas died in two separate clashes with soldiers.

The political violence comes as President Andres Pastrana, who's made achieving peace his top priority, prepares to travel to Washington on Tuesday.

It will be the first state visit by a Colombian president in more than two decades.