Washington, Aug 10 (DPA) The US commander has announced a change of strategy in Afghanistan, warning that insurgents with the Islamist extremist Taliban had made advances in the country, according to a media report Monday.

Quoting an interview with General Stanley McChrystal from Saturday, the Wall Street Journal said the Taliban have been able to make strikes outside their normal strongholds in the south of the country and threaten previously peaceful regions in the north and the west.

'It's a very aggressive enemy right now,' McChrystal said.

'We've got to stop their momentum, stop their initiative. It's hard work,' he said, adding that casualties among US troops were liable to be high for several months.

Speaking from a NATO base in Kabul, McChrystal said his new strategy was to concentrate more troops in threatened cities and populated areas, naming specifically the Taliban stronghold of Kandahar.