KABUL (Reuters) - NATO-led forces in Afghanistan are investigating reports that an Afghan soldier had shot several of its troops in Afghanistans volatile south, the coalition said on Saturday. If the incident is confirmed, it would be the latest in a series of rogue attacks by Afghan police and soldiers, underlining the pressure on US and NATO troops as they try to train Afghan forces rapidly to allow the handover of security responsibility. Afghan media reported the soldier had killed up to three members of the NATO-led ISAF in the Sangin district of southern Helmand province, a Taliban stronghold, late on Friday. It quoted a Taliban spokesman as saying the Afghan soldier had fired on the foreign troops inside a military base and had then fled to join up with Taliban fighters in the area. We are aware of the incident in Helmand and we are investigating the incident, an ISAF spokesman said. He said no information would be released until the investigation was complete. U.S. and British troops make up the backbone of the NATO forces in the area.