Laborers at Colombia's main coal railway went on strike over pay and working conditions, the company and a senior union official said, threatening to paralyze more than one-half of shipments from the world's fourth largest exporter of coal.

Stoppage in Colombian output from the strike and another walkout at a Prodeco mine, owned by Glencore's Prodeco unit, will have to be prolonged to lift prices as both Atlantic and Pacific markets are oversupplied despite a strong coal burn across much of Europe and steady imports into India and China.

Workers at the Fenoco railway -- mainly those who perform maintenance on the line -- went on strike at 6 a.m. local time on Monday, Ricardo Machado of the Sintraminergetica union told Reuters by telephone.

The company confirmed a strike had begun.

The train has a capacity of 42 million tons per year.

Shareholders in the company include Glencore International Plc's Prodeco unit, Drummond Co Inc and Goldman Sachs Group Inc's Colombian unit. The mining firms are among the top coal producers in Colombia.

Last week, Colombian coal miners walked out at the La Jagua mining complex of Glencore's Prodeco unit after failing to reach a compensation deal. (Reuters)