A roadside bomb in southern Afghanistan killed four civilians while an operation by U.S.-led forces left three people dead and a woman and child wounded on Monday.

The bomb struck the civilian's vehicle and also wounded three civilians inside in Zabul province, said Jalani Khan, a provincial police official. He blamed the Taliban for planting the bomb.

Separately, U.S.-led troops killed three men and wounded a woman and a child during a raid against a Taliban commander in southern Helmand province Monday, the force said in a statement. It did not say whether the men were armed militants or civilians.

The wounded woman and child were transported to a coalition hospital for treatment.

Southern Afghanistan is the center of the Taliban-led insurgency. President Barack Obama has ordered 21,000 new American troops into Afghanistan, hoping to reverse Taliban gains.

Meanwhile, NATO-led troops in eastern Afghanistan seized and destroyed 2.24 tons (2 tons) of pure heroin valued at $3 million, the military alliance said in a statement Monday.

Troops discovered the heroin after searching a suspicious vehicle in the country's east, NATO's International Security Assistance Force said. It did not identify the province or the exact date when the drugs were found.

U.S. and other Western officials have said the booming drug trade is funding the Taliban's insurgency in Afghanistan and undermining governance.