Marines' 'most significant encounter' against Taliban

KABUL, Afghanistan (CNN) - U.S. Marines continued to lead a major push against militants in southern Afghanistan on Friday in an attempt to rout the Taliban from their stronghold in Helmand province, Marine Capt. William Pelletier said.

A Marine source described the fighting Thursday evening as "our most significant encounter."

Sporadic fighting took place over several hours in the southeastern sector of Garmser district, said Pelletier, spokesman for the Marine Expeditionary Brigade-Afghanistan.

Helmand province, a poppy-growing region, is the focus of the military push called Operation Khanjar. Afghanistan supplies 90 percent of the world's opium - which is used in the production of heroin.