US warns citizens of Afghan protests Friday The US embassy in Kabul has warned Americans in Afghanistan of possibly violent protests Friday in which Westerners could be targeted over the burning of Korans at a military base. The "emergency message" urges Americans to "shelter in place and avoid any unnecessary movement," with at least one demonstration reportedly planned for the capital Kabul and more possible after Friday prayers. "Road closures are expected and it is possible the protests will become violent," the message says, warning that places where Westerners congregate should be avoided. "We wish to remind US citizens that past demonstrations in Afghanistan have escalated into violent attacks on Western targets of opportunity," the message says. The warning comes after three days of violent protests across the country over the burning of Korans at the US-run Bagram airbase north of Kabul killed 14 people, including two American soldiers. Thousands of furious Afghans have attacked French, Norwegian and US bases, shouting "death to America" after Taliban insurgents exhorted their countrymen to kill foreign troops to avenge the incident. US President Barack Obama was forced to apologise in a letter to Afghan President Hamid Karzai, expressing "deep regret" for the incident, which he said was unintentional, and pledging that those responsible would be held accountable. Karzai said a US officer was responsible -- "out of ignorance" -- for the Koran burning and that the US government had admitted the mistake, his office said. Afghanistan is a deeply religious country where slights against Islam have frequently provoked violent protests.