About 4,000 US marines, supported by 650 Afghan troops, have launched a major offensive against the Taliban in the Southern Afghanistan province of Helmand.

The offensive, the first big push by marines since their deployment in Afghanistan and the first key mission under the new presidency, has been codenamed Khanjar or ‘Strike of the Sword’.

US forces began the offensive early Thursday morning assisted by heavy transport vehicles, helicopters and NATO aircraft providing air cover.

US military spokesman Captain William Pelletier told the BBC that there had been no enemy contact in the first hours of the operation but that a marine was slightly injured when an improvised explosive device detonated in the village of Nawa.

The operation is intended to disrupt the Taliban in what is considered their stronghold and also to improve security ahead of the 20 August presidential elections.

The action comes only two days after US forces withdrew from big cities and towns in Iraq, meeting the 30 June deadline set by the Bush administration.

President Obama has pledged to send an additional 21,000 soldiers to Afghanistan, many of whom will be redeployed from Iraq.