KABUL - At least four US soldiers were feared dead when a NATO helicopter crashed overnight in restive southern Afghan Helmand province, an Afghan official said on Friday.

"Initially, there was a suicide attack in Lakani area of Garmsir district at about 8 pm local time Thursday, leaving four Afghan policemen dead and seven policemen injured and a US helicopter was en route to lift the injured," a district official told Xinhua, adding the helicopter was crashed near the Lakani area of the district due to poor weather conditions in the area.

The official who declined to be named said that at least four US soldiers were feared dead in the incident.

Meanwhile, the NATO-led International Security Assistance Force (ISAF) confirmed the incident.

"The crash site is secured; the cause is under investigation," the military alliance said in a statement.

"Additional information will be released as appropriate," the ISAF said in a brief statement without providing more details.