Kabul, Afghanistan (CNN) -- A large crowd swarmed a military base and numerous demonstrations turned deadly Friday in Afghanistan, the fourth day of fallout after NATO troops burned Qurans at a military base, officials said.
One of the protests took place just outside a U.S. consulate.
The developments came a day after U.S. President Barack Obama apologized for the incident at Bagram Airfield this week, calling it an unintentional error.
At least eight people were killed and 27 wounded in protests Friday, mostly in Herat province, officials said. The death toll includes six in Herat, one in Baghland and one in Nangahar, according to Sediq Sediqqi, spokesman for the Interior Ministry. Seven of the wounded were in Kabul, and they included three police officers, a spokesman for the Health Ministry said.
NATO's International Security Assistance Force (ISAF) said there were no reports of ISAF personnel wounded in the protests.
The commander of ISAF and U.S. forces in Afghanistan, Gen. John Allen, addressed the issue in a visit to troops at a military base where two U.S. soldiers were killed Thursday by a man wearing an Afghan National Army uniform. A protest over the burning of Qurans was taking place outside the base at the time of the killings.
"Now is not the time for vengeance," he said. "Now is the time to look deep inside your souls, remember your mission, remember your discipline, remember who you are. We'll come through this together as a unit."
He called on troops to "show the Afghan people that as bad as that act was at Bagram, it was unintentional, and Americans and ISAF soldiers do not stand for this. We stand for something greater than that."
Gen. Sher Mohammad Karimi, the Afghan National Army's chief of staff, joined Allen on the trip and thanked the troops for their "sacrifices for humanity, not just the Afghan people."
NATO posted a video of the visit on its official YouTube channel, without naming the base.
Hundreds of people attacked an ISAF base in Pul-i-Khumri in northern Baghlan province Friday, destroying a security fence and parts of the walls, according to an Afghan National Army official.
Police interfered and started shooting into the air. One civilian was killed and 11 others were injured, the official said.
ISAF had no immediate comment on that incident.
The demonstrations in Herat province took place in several different locations. One was in Herat city near the U.S. consulate, said Mohayddin Noori, spokesman for Herat's governor.
A witness said demonstrators were setting vehicles on fire, including police cars.
There were also protests in the Adraskan and Shindand districts, Noori said.
A spokesman at a local hospital said a total of nine injured people were brought in.
In other parts of the country, demonstrations were generally peaceful Friday morning, Interior Ministry officials said.
In a letter delivered to Afghan President Hamid Karzai Thursday, Obama called the act "inadvertent," Karzai's office and National Security Council spokesman Tommy Vietor said.
"We will take the appropriate steps to avoid any recurrence, including holding accountable those responsible," Obama said in the letter delivered by Ryan Crocker, the U.S. ambassador to Afghanistan.
NATO troops incinerated Islamic religious material at Bagram Airfield earlier this week.
A military official said the materials 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."
Muslims believe the Quran is the word of God, so holy that people should wash their hands before even touching the sacred book.
CNN's Josh Levs contributed to this report.