U.S. and Afghan troops Saturday advanced into the Taliban heartland in southern Afghanistan in the first major offensive after U.S. President Barack Obama's Wednesday announcement of troop surge in the insurgency-ridden country.

The operation dubbed "Cobra's Anger", according to the statement, began Friday in the Nawzad district of Helmand province, with the involvement of some 1,000 U.S. Marines and 150 Afghan soldiers to disrupt Taliban supply and communications lines in the region.

"So far as a result of the operation four militants have been killed and two were detained," the Afghan Defense Ministry said Saturday in a statement, adding that the operation is scheduled to last for four days.

The troops reportedly met little resistance from insurgents Saturday. No U.S. or Afghan casualties have been reported.

Nowzad is one of the hotbeds of hard-core Taliban militants in Helmand known as the Taliban safe haven and notorious for growing poppy in Afghanistan.

The operation is one of several large offensives that U.S. Marines have carried out since July, when 4,000 of them seized the lower Helmand River valley.

The offensive came on the same day when NATO and partner nations pledged an extra 7,000 military personnel for Afghanistan, in response to Obama's call for an international military surge in the country.

Obama on Wednesday unveiled his long-deliberated new strategy on Afghanistan by sending 30,000 troops, which will start arriving in Afghanistan in the coming months.

Deploying extra troops, combined with the growing Afghan National Army and police would enable the U.S. and allies to have about 300,000 security forces on the ground next year, outnumbering the Taliban insurgents by over ten-to-one, according to estimation.

According to media reports, a majority of the additional U.S. troops will be deployed in southern provinces, where the Taliban are most active.

Obama in his strategy for Afghanistan set July 2011 as the start date for withdrawal of U.S. forces from Afghanistan. However, U.S. Secretary of Defense Robert Gates and U.S. Secretary of State Hillary Clinton told the Congress the date could be changed depending on the situation on the ground.