Kabul, Afghanistan (CNN) -- Afghans protesting the reported deaths of civilians in a NATO airstrike clashed with police in northern Afghanistan on Wednesday, leaving at least 12 dead and 83 wounded, local authorities said.
The demonstrations took place near the offices of a German provincial reconstruction team in Takhar province, north of Kabul. Provincial government spokesman Faiz Mohammad Tawhidi blamed armed protesters for starting the bloodshed, saying some of the demonstrators "turned to violence for their own goals."
"They opened fire on protesters and security forces, and they threw grenades among the protesters and on the PRT," Tawhidi said. Some of the victims died in an exchange of fire between the protesters and security forces, he said.
About 4,000 people attended the demonstration, Takhar Gov. Abdul Jabar Taqwa said earlier. Two German soldiers and four Afghan guards were injured during the clashes, according to the German military.
The protest was sparked by a Tuesday night attack that NATO said killed four insurgents, including two armed females.
According to NATO, a joint Afghan-allied operation Tuesday night targeted "the facilitator" of the Islamic Movement of Uzbekistan, an operative "heavily involved in the movement and procurement of weapons for imminent attacks."
But a deputy governor said the victims of the attack included a man, his wife and a guest not linked to any insurgent group.
The protesters "were ordinary and innocent residents of the village," said Farid Zaki, the deputy governor. "These night raids are creating mistrust between the people, the Afghan government and international forces."
Afghan President Hamid Karzai issued a statement condemning the NATO attacks and demanding a detailed explanation from NATO commanders. He said the Afghan government would investigate the incident.
CNN's Mohammed Jamjoom and Matiullah Mati contributed to this report.