A total of 75 international soldiers were killed in July, most of them in Helmand.

The US marines also provided helicopter lifts and other aviation support for Wednesday's mission, the US military statement said.

Afghan election commission officials said earlier this week that due to security concerns, the commission would not be able to hold elections in around 10 districts unless Afghan and NATO forces provide enough security there.

At least four of the 10 districts are in Helmand province, but given the short time before the vote, it was unlikely that security forces could fulfil the commission's demand.

More than 100,000 international troops and around 200,000 Afghan security forces are to provide security for more than 6,500 polling centres on election day, the second in Afghanistan's recent history.