At least two people have been killed and 20 injured in Afghanistan in the second day of protests over the burning of copies of the Koran.
One person died in Kabul and one in Jalalabad in demonstrations where shots were fired.
There were demonstrations in Kabul and the eastern city of Jalalabad.
On Tuesday, the US commander in Afghanistan, Gen John Allen, apologised after Korans were "inadvertently" put in an incinerator at Bagram airbase.
US officials reportedly believed Taliban prisoners were using the books to pass messages to each other.
The charred remains of the volumes were found by local labourers.
Pro-Taliban slogans
Protesters in Kabul shouted, "Death to America!" and threw stones at Camp Phoenix, the main US base in the city.
A doctor in Jalalabad told the BBC one protester had been killed and 10 injured. Another 10 were wounded in Kabul.
Witnesses at the protests in Kabul said security guards were firing into the air. There were also reports of people chanting pro-Taliban slogans.
Demonstrators blocked the road linking Kabul with Jalalabad, one of the main trade routes into the Afghan capital.
Riot police used water cannon to disperse protesters, the AFP news agency reported from Kabul.
One protester, 18-year-old Ajmal, told Reuters: "When the Americans insult us to this degree, we will join the insurgents."
The US embassy in Kabul has tweeted that it is on lockdown and all travel is suspended.
"Everyone is emotional," Kabul resident Mohammad Naseer Malikzai told the BBC. "I am hurting and disappointed.
"I created a Facebook group where I was disputing with a lot of people. The American apology is useless."
US Defence Secretary Leon Panetta said he and Gen Allen apologised to the Afghan people "and disapprove of such conduct in the strongest possible terms".
After previous incidents, many Afghans find it hard to understand how US forces could have allowed the Koran to have been burned, says the BBC's Andrew North, in Kabul.
Afghanistan is a very religious country, he adds, but also one where many people are illiterate and susceptible to attempts to whip up anger.
Muslims consider the Koran the literal word of God and treat each book with deep reverence.
The Nato-led Isaf force is now investigating the incident, a spokesman told the BBC.
"It was the local workers who discovered the nature of the material and therefore stopped worse things from happening," said Brig Gen Karsten Jacobson.
"But it was a mistake and that's what we're investigating at the moment, how did this come to be, what orders were given?
"But at the end of the day we have to stand to the fact a mistake was made and the commander apologised."
Last year, at least 24 people died in protests across Afghanistan after a hardline US pastor burned a Koran in Florida.
On Tuesday, one person was wounded and five detained after troops at Bagram, 60km (40 miles) north of Kabul, fired rubber bullets at protests.
Bagram includes a prison for Afghans detained by Nato forces.
http://www.bbc.co.uk/news/world-asia-17123464