A U.S. Marines commander said Wednesday his troops have killed 400 insurgents in southern Afghanistan since late April.

Col. Peter Petronzio, the commander of the 24th Marine Expeditionary Unit, said the figure came from the governor of the southern Helmand province where his troops have been deployed since late April.

Some 2,200 U.S. Marines moved into the town of Garmser in Helmand province to clean the area of insurgents.

Helmand province is the world's largest opium poppy growing region, the main ingredient in heroin. It is also the area with the highest level of insurgent activity in the country.

After months of fighting around Garmser, Petronzio said the area is not yet secure but is more stable.

"The Taliban proved they wanted to fight for Garmser and we took the fight to them," he told a news conference in Kabul.

Petronzio said NATO and Afghan forces are committed to completing their mission in an area that is an important gateway for insurgent fighters smuggling weapons from Pakistan.

"If the Taliban are waiting for us to leave, they will have a very long wait," he said.

More than 2,100 people — mostly militants — have been killed in insurgency-related violence in Afghanistan this year. More than 8,000 people died in attacks last year, according to the United Nations, the most since the 2001 U.S.-led invasion.

Last week the Pentagon announced it has extended the tour of the 2,200 Marines in Afghanistan, after insisting for months the unit would go home on time. The unit will stay an extra 30 days and go home in early November rather than October, officials said.