Three coal trucks were torched on Sunday at Colombia's Cerrejon mine, where miners have been on strike for the last two weeks, according to the Swiss-British-Australian consortium running the site.
The consortium said in a statement that three trucks had been completely burnt and another partially destroyed as a result of a bomb attack at the mine in the far north of the country, near the border with Venezuela.
The consortium, consisting of the Swiss Xstrata, Britain's Anglo American and Australia's BHP Billiton, said no one was wounded in the incident but condemned the "terrorist" attack and urged workers to reject such actions.
Cerrejon is one of the world's largest open pit coal mines. Last year 34.6 million tons of coal were extracted from the site, and the consortium aims to extract 98 million tons this year.
On February 7 some 4,000 workers and 7,000 subcontractors went on strike, demanding new two-year contracts with higher pay and safer working conditions.
The Labor, Mining and Energy Ministry has urged the two sides to negotiate anew and offered to help mediate.
The firm has said it loses $3 million every day the workers are on strike.
Colombia's President Juan Manuel Santos views mining as a key source of economic growth for the Andean nation, which is Latin America's largest coal producer.