Afghan authorities braced for a fourth day of violent protests after Friday prayers over the burning of copies of the Koran by the US military, despite calls for calm from the president and an apology from US President Barack Obama, DPA reported.
"We are extra vigilant," Interior Ministry spokesman Sediq Sediqqi said.
"We've had two reports of demonstrations, small demonstrations. But it's OK now. Nothing to worry about," Sediqqi said. "The police are on alert, of course."
Riot-control police had been deployed in Kabul, officials said.