Updated

Firefights broke out between NATO forces and Afghan police in two parts of Afghanistan overnight, with four Afghan officers killed in one of the incidents, officials said Wednesday.

In southern Kandahar province, Afghan police and NATO troops clashed in Arghandab district — a farming community just outside of Kandahar city, said Shah Mohammad, the top official for the district. He said four Afghan police officers were killed and four wounded.

It was not clear what started the firefight and Mohammad said that investigators had been dispatched to the site to investigate the cause.

"Right now we only have this very sad news from there," Mohammad said.

A NATO spokesman confirmed that there was "an incident" in Arghandab, but did not provide further details. Capt. Justin Brocckhoff said more details would become available after an investigation.

In the eastern province of Ghazni, meanwhile, NATO forces fought briefly with Afghan police manning a checkpoint in Ghazni city before the two groups realized the mistake.

The NATO troops approached the checkpoint while on a nighttime patrol through the area, provincial Police Chief Gen. Zarawar Zahid said. The Afghan police saw armed men and asked them to stop and started firing when the NATO troops did not, Zahid said.

The exchange of gunfire lasted about 15 minutes and no NATO or Afghan forces were killed, Brockhoff said. He said an investigation had also been launched into that incident.

Meanwhile, a police inspector was shot dead in Kandahar city Tuesday night by unknown gunmen, said Deputy Police Chief Shershah Yousafzai. Yousafzai said they suspected he was killed by militants. The Taliban has repeatedly targeted Afghan forces and police.