Five British soldiers were killed and six others sustained injuries in Afghanistan's southern restive region, a press release of the NATO-led International Security Assistance Force (ISAF) said Wednesday.

"Four U.K. soldiers were killed, another one died of his wounds, and a further six were injured while conducting operations in Southern Afghanistan Tuesday," the press release added.

Two Afghan National Police officers were also wounded, it further said.

However, it did not give more details on the exact place of the incident. But it added that a joint ISAF and Afghan Ministry of Interior team is investigating the incident due to allegations the British soldiers may have been fired upon by Afghan security forces.

Meantime, a local who declined to be identified told Xinhua that the incident occurred Tuesday afternoon in Zarghon village of Nad Ali district, Helmand province, when a police officer from a nearby checkpoint opened fire on the British patrol team killing five soldiers and troops returned fire killing two policemen.

However, local officials are reluctant to make comment on the incident.

More than 8,000 British troops with majority of them deployed in Helmand province have been serving in Afghanistan within the framework of NATO-led peacekeeping force.