Kabul, Afghanistan (CNN) -- NATO and Afghan troops are probing a report that an Afghan soldier fatally shot three American troops recently in southern Afghanistan, authorities said on Saturday.
NATO's International Security Assistance Force confirmed a joint probe, and the Afghan army's chief of staff in Helmand province, Zamin Hassan, told CNN it is aware of ISAF fatalities in Helmand's Sangin district and have sent a delegation to investigate.
They declined further comment.
According to a Taliban statement that surfaced on militant websites Saturday, the Afghan soldier fired at the troops at a U.S. base in Sangin district late Friday.
Separately, two NATO-led troops were killed during insurgent attacks in different parts of Afghanistan on Saturday. One death occurred in the east and the other in the south.
The force said it defers identification of casualties to the relevant national authorities, and it did not identify the precise location of the strikes.
In northern Afghanistan, the death toll from a suicide bombing has increased to 12, a spokesman for the governor of Faryab province said Saturday. At least 26 were injured in the attack at a crowded marketplace that targeted the head of the provincial council.
CNN's Matiullah Mati and Pierre Bairin contributed to this report.