Violence over the burning of copies of the Quran by NATO troops at a military base in Afghanistan has spread, prompting the US president to issue an apology and the Afghan government to demand trial and punishment for those responsible.
As protests over the incident continued for a third day on Thursday, the death toll of Afghan demonstrators rose to 12.
In a separate incident, two US soldiers were killed when an "individual wearing the Afghan army uniform" opened fire on them at a military base in Khogyani in eastern Nangarhar province, Mohammad Hassan, the district's governor, told the AFP news agency.
"As the protesters approached the American base here, an ANA [Afghan] soldier in the base opened fire on American soldiers, killing two soldiers," Hassan said.
Barack Obama's written apology came shortly after Hamid Karzai, Afghanistan's president, said a US officer was responsible for the Quran incident.
The US embassy in Kabul was locked down on Wednesday and remained closed on Thursday.
The embassy said on Twitter that "peaceable assembly is an American value/tradition; we join President Karzai in urging restraint and nonviolence today".
Obama's 'deep regret'
Karzai's office said it received a letter in which Obama expressed his "deep regret for the reported incident" and offered his "sincere apologies".
According to the statement, Obama wrote: "The error was inadvertent; I assure you that we will take the appropriate steps to avoid any recurrence, to include holding accountable those responsible".
However, in what could further intensify the unrest, the Taliban issued a statement calling on the Afghan people to "target the military bases of invader forces, their military convoys and their invader bases".
The statement, issued via email by a spokesman named Zabiullah Mujahid, called on Afghans to give NATO troops "a lesson to never dare desecrate the holy Quran again".
|Afghans protested across the country for the third day on Thursday over the burning of the Quran [EPA]
Despite telling the public to "not stop" at protests, Mujahid said the calls against foreign military forces would not affect the anti-government group's negotiations with US officials in Doha.
"We condemn the desecration of the Holy Quran in the strongest terms, but this issue will not affect this process in Qatar," he said.
The disturbances began after reports earlier in the week of the discovery by local labourers of charred copies of the Quran as they collected rubbish at the US-run Bagram base in Parwan province.
Protests continued on Thursday in the Kart-e-Naw and Bagrami districts of Kabul, with several hundred turning out with banners reading "Long live Islam, long live the Quran".
In Laghman province, over 600 people marched into the provincial capital of Mihtarlam chanting "Death to America".
Afghan sources said the protests in Laghman had turned violent and had been growing since the early hours of the morning.
A police official speaking to the AFP news agency said thousands of protesters besieged the headquarters of a provincial reconstruction team (PRT) in the provincial capital.
"People had come from all over Laghman. They attacked the PRT, they climbed up the walls, they set fire to something there, I think a container," the police official said.
Protests in Jalalabad
In the country's east, 300 students took to the streets of Jalalabad, according to reports.
North of Jalalabad, fresh protests rocked the city of Asadadab in the province of Kunar, while there were also reports of protests in Khost province.
Protests spread to the north as people took the streets of Faryab, where hundreds gathered in the provincial capital, and Badakhshan provinces.
The protests on Wednesday caused seven deaths and left 32 people injured, according to Afghan government sources.
Before Obama issued his apology, Leon Panetta, the US defence secretary, had issued his own, in addition to backing the call for "swift and decisive action to investigate this matter" by the US commander of NATO forces in Afghanistan, General John Allen.
"These actions do not represent the views of the United States military. We honour and respect the religious practices of the Afghan people, without exception," Panetta said.