KANDAHAR: A roadside bomb planted by the Taliban killed 11 civilians in Afghanistan's southern province of Helmand on Sunday, the provincial administration said.

The dead included two children and two women, provincial governor's spokesman Daud Ahmadi told AFP, blaming the Islamist militant movement after a car struck the device in Nawzad district, in the north of Helmand.

Thousands of US, NATO and Afghan troops have been pursuing a major offensive against the Taliban in Helmand's Marjah and Nad Ali areas since February 13.

Helmand is the most troubled region in Afghanistan with the highest level of activity by insurgents, mostly remnants of the Taliban ousted from government by US-led forces in late 2001.

The current operation, called Mushtarak (Dari for "together"), is aimed at driving the Taliban from their strongholds and is part of Washington's new war strategy for Afghanistan announced late last year.

The town of Marjah continues to see sporadic resistance.

Over a dozen foreign soldiers and at least two of their Afghan counterparts have been killed during Mushtarak. Dozens of insurgents have also died although the authorities have yet to give a precise figure.

At least 15 civilians have also been killed in the offensive, 12 of them by a rocket fired by US forces and intended to hit insurgents.

Operations are set to expand to other Taliban bastions, particularly in the neighbouring province of Kandahar, where the militants maintain a large presence.

Also on Sunday, one security worker was killed in main Qalat town of Zabul province when his vehicle was hit by a similar bomb, Mohammada Jan, a provincial spokesman said.

Elsewhere in Zabul five insurgents were killed during clashes between Afghan security forces and militants, the spokesman added.

About 121,000 international troops, mainly from the United States and NATO, are stationed in Afghanistan fighting the Taliban.