At least 80 people are dead and more than 18,000 have been forced to flee their homes in Colombia, officials say, amid fierce clashes between two rival armed groups on the border with Venezuela.

The death toll from attacks by a rebel group in Colombia's Catatumbo region has risen to 60, the country's human rights office has said. Rival factions have been vying for control of the cocaine trade in the region - which sits near the border with Venezuela - for years.