Kabul, Afghanistan (CNN) -- A protest over the burning of Qurans at a U.S. base turned violent Sunday, leaving a protester dead and several U.S. service members and police wounded, officials said.
The violence in northern Kunduz province came a day after a gunman killed two U.S. military officers inside the highly secured Afghanistan Ministry of Interior.
U.S. officials have said the burning of the Muslim holy books was inadvertent.
The demonstration Sunday -- the sixth day of protests -- began peacefully, said Kunduz police spokesman Sayed Sarwar Hussaini. But it soon turned violent as demonstrators attacked the police chief's office and a U.S. military site.
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Protesters threw a hand grenade at the base, injuring seven U.S. military personnel believed to be Special Forces members, Hussaini said. NATO's International Security Assistance Force had no immediate comment on the number of wounded or their roles in the military.
Capt. David Yaryar, an ISAF spokesman, said there was an explosion and then small arms fire at the site, and that several ISAF personnel were wounded and evacuated for medical care.
The attack took place at Combat Outpost Fortitude, ISAF said.
Sixteen police were injured in the attack at the police chief's office, said Hussaini. Protesters used grenades, pistols, knives, sticks, and stones, he said.
One protester was killed and three were injured in the demonstration in Kunduz, Hussaini said.
Separately, Afghan and coalition forces captured Taliban leaders in several provinces, including Kunduz, Sunday, ISAF said.
The incidents came after Afghanistan President Hamid Karzai called for calm.
While the "emotions of our people" over the burned Qurans "are legitimate and valuable," Karzai said in a televised address, remaining calm would help stop "enemies of our peace and stability" from taking advantage of the situation and harming people and property.
At least 29 people have been killed and nearly 200 wounded in recent protests, Karzai said. The protester in Kunduz brings the death toll to 30.
Two U.S. soldiers were gunned down last week at a base in eastern Afghanistan by a man wearing an Afghan National Army uniform.
The man who shot two military officers Saturday at the interior ministry was a junior intelligence officer with ties to a Pakistani religious school, an Afghan counter-terrorism official said.
The gunman was identified as Abdul Saboor, an employee in the ministry's intelligence department, according to the official, who spoke on condition of anonymity because he was not authorized to release the information.
"We believe it was 100% linked to the Quran burning because of the religious background of this junior officer. He spent two months in a Pakistani madrassa," the official said.
The interior ministry confirmed that the gunman in Saturday's shooting is believed to be one of its employees, whose "whereabouts are unknown." Police "are making every effort to find him as soon as possible," the ministry said.
The Taliban claimed responsibility for the shooting Saturday. A Taliban spokesman gave the same first name for the shooter that the counter-terrorism official gave Sunday. But the official did not say whether the alleged gunman was affiliated with the Taliban.
Karzai extended his condolences to the families of the American officers killed, but said he did not know who was responsible or what was the motivation.
Karzai also repeated calls for the United Sates to prosecute those responsible for burning the Qurans.
"We have asked for punishment and an investigation," he said.
U.S. Secretary of State Hillary Clinton told CNN, "We are hoping that voices inside Afghanistan will join that of President Karzai and others in speaking out to try to calm the situation."
"It is out of hand and it needs to stop," she said.
U.S. Ambassador to Afghanistan Ryan Crocker, in an exclusive interview with CNN, said in cases like this, the anger generally "tapers off and I think we're all hopeful that the appeal for calm that President Karzai made today -- and he did so with the backing of the entire political leadership of the country -- will create a condition in which this diminishes. There were some tough attacks up in the north. The rest of the country, though, was pretty calm today."
The protests began last week after reports emerged that NATO troops burned Qurans at Bagram Airfield.
A military official said the materials burned were removed from a detainee center's library because they had "extremist inscriptions" on them and there was "an appearance that these documents were being used to facilitate extremist communications."
The official spoke on condition of anonymity because of the sensitivity of the issue.
American officials, including President Barack Obama, have apologized and said the burning of the Qurans was an unintentional error.
Muslims believe the Quran is the word of God, so holy that people should wash their hands before touching the sacred book.
Saturday's killing of the American officers prompted Gen. John Allen to order several hundred ISAF advisers to withdraw from ministries in Kabul as a precaution, raising questions about a U.S. military plan that plans to focus on the use of small teams of military advisers as it withdraws troops.
The United States also pulled embedded civilians out of ministries, Crocker said.
France announced Sunday that it was withdrawing all French public officials in Afghan institutions temporarily to ensure their safety.
ISAF said initial reports about Saturday's incident indicated that "an individual" turned his weapon against NATO service members, later confirmed by an Afghan police official to be an American colonel and major.
"We are aware of the media reports that are out there now, naming a suspect, but we have no new information from our ongoing investigation of yesterday's incident, regarding the shooter," said Lt. Col. Jimmie Cummings, an ISAF spokesman.
Saboor, according to the Afghan counter-terrorism official, arrived at the ministry Saturday about noon, signed himself in and retrieved his gun.
The two officers were found dead in their office from gunshot wounds to the head, said an Afghan police official, who also spoke on condition of anonymity because he was not authorized to discuss the incident with the media.
Despite being pulled from the ministries, the military advisers remained in contact with ministry personnel, Cummings said.
"We will not let this incident divide the coalition," he said.
Even so, NATO troops working as advisers outside the Afghan capital were also warned to take precautions.
The warning follows the shooting deaths last week of two American soldiers by a man wearing an Afghan National Army uniform at a base in the eastern Nangarhar province.
A protest over the burning of Qurans was taking place outside the base at the time of the killings.
The Defense Department over the weekend identified the two as Army Sgt. Joshua A. Born, 25, of Niceville, Florida, and Cpl. Timothy J. Conrad Jr., 22, of Roanoke, Virginia. Both were assigned to the 385th Military Police Battalion, 16th Military Police Brigade at Fort Stewart, Georgia.
Amid the protests, ISAF said Sunday its efforts against the Taliban continue to move forward across Afghanistan.
Afghan and coalition security forces captured Taliban leaders in Kandahar province and Ghazni province, and a commander with the insurgent Haqqani network in Logar province, ISAF said in its operational update.
Crocker, in the CNN interview, talked about having opened the U.S. embassy in Kabul more than 10 years ago when "there was nothing, no institutions no ministries, no police, no army, no nothing." Now, "while the challenges are huge, the achievements are pretty considerable, too," and the stakes remain high, he said. "If we decide we're tired of it, al Qaeda and the Taliban certainly aren't."