Nearly 4,000 Marines launched the operation on Thursday in parts of the southern province of Helmand, suffering their first fatality in a pivotal test of President Barack Obama's aggressive new strategy against the Taleban.

The 1/5 Infantry Battalion met only light resistance in their push south and had already been able to meet locals at shuras (councils), Brigadier General Larry Nicholson said, speaking to a convoy with which AFP was travelling.

But 'for 2/8 there is a hell of a fight going on in the southern quarter of the sector,' the top Marine said on arrival at Garmsir, a town along the Helmand River that was a key objective for Operation Khanjar.

'2/8 are going to face some challenges,' he said. The battalion was in an area called Toshtay about 25 kilometres south of Garmsir.

Commanders said they would persuade locals that the Afghan security forces - backed by Western troops - offered them a better long-term future than the fundamentalist Taleban militia as Afghanistan braces for elections next month.

On Thursday Marines were inserted into Garmsir and Nawa with little resistance, and quickly overran Khanishin further south where the Taleban had set up a proxy government and justice system.

But they also recorded their first death in an air and land assault that is the Marines' biggest operation since in Fallujah in Iraq in November 2004.

Troops had on Thursday destroyed a militant position in Garmsir, BG Nicholson said.

'An enemy-controlled baseline just south of Garmsir was crushed yesterday but that doesn't mean all the enemy have gone,' he said.

'In the next few days the enemy will observe us to see what we are doing.

Then they will come back with a vengeance,' he said.

BG Nicholson later told AFP separately: 'Garmsir is three-quarters quiet but there is fighting in Toshtay. We intend to clear that up today. This doesn't mean it is over. The enemy may be reassessing the situation.' -- AFP