A senior US military official has told NBC News that the Nato soldier killed by an Afghan Local Police officer in the east of the country was an American.
Earlier two British troops were shot dead by an Afghan soldier.
16 Nato servicemen have been killed by Afghan Security forces so far this year.
More top news
Judges will rule if Brexit talks can start without consent from MPs and without formal input from legislatures in Wales, NI and Scotland.
Another cold night across much of England and Wales. Milder conditions pushing into the west of Ireland and Scotland.
US officials have denied that the US military is coordinating with Russia in Syria.