Kabul, Afghanistan (CNN) -- Four people were shot dead Friday in an anti-NATO demonstration in southern Afghanistan during an exchange of gunfire that took place amid a protest over civilian casualties, police said.
The violence erupted in Qalat -- the provincial capital of the country's southern border province of Zabul -- and left three civilians and one police officer dead, according to the provincial police chief, Abdul Elham.
Five others were injured in the firefight, he said.
Elham did not offer details regarding the previous civilian casualties, which allegedly occurred the night before, and it's not clear how Friday's protest turned deadly.
NATO officials acknowledged troops took part with Afghan security forces in a raid targeting Taliban insurgents that spanned Thursday night into Friday morning.
The insurgents are believed to have escaped through a municipal irrigation channel, according to International Security Assistance Force spokesman Capt. Pietro D'Angelo.
He said that NATO is not aware of any civilian casualties that resulted from the raid, but local officials say that the following morning hundreds took to the streets in protest.
Meanwhile, NATO reported that three service members were killed in separate incidents in southern Afghanistan. No details about their deaths were reported.
As of Friday, at least 1,577 U.S. soldiers have died in Afghanistan since the 2001 invasion, according to Defense Department figures. The total number of NATO troops killed since the war began is 1,680.