Militants have attacked security forces near the presidential palace in the centre of the Afghan capital, Kabul.
A BBC correspondent says the assailants are embroiled in clashes with President Hamid Karzai's bodyguards, as well as security personnel from the nearby ministry of defence and a CIA station.
The Taliban have said they are carrying out the attack.
The incident comes only days after Mr Karzai raised objections about US-backed peace talks with the Taliban.
He said the High Peace Council, the government body set up to lead peace efforts, would not take part unless the process was "Afghan-led".
The attack near the presidential palace, in the area of Shash Darak, began at about 06:30 local time (02:00 GMT), witnesses and police said.
The militants initially targeted the palace's eastern gate, where dozens of journalists had gathered for a news conference with President Karzai.
The BBC's Bilal Sarwary, who was among the crowd of journalists, says they were forced to run for cover as bullets flew overhead.
The journalists heard several explosions, and reports said grenades were being thrown.
The Nato-led International Security Assistance Force (Isaf) wrote on Twitter: "Small arms fire and multiple explosions reported in #Kabul. Situation developing."
The CIA station and the Afghan ministry of defence are among the many official buildings and embassies situated near the palace.
It is not clear whether the president was at the palace when it came under attack.(BBC)