A suicide bomb and gun attack is ongoing in the centre of the Afghan capital Kabul, with a string of blasts targeting the US embassy and Nato's Isaf headquarters.Gunmen are holed up in a partly-built high-rise building nearby, exchanging sporadic gunfire with police.
The Taliban say that they are behind the attack.It comes weeks after suicide attackers stormed the city's British Council office, killing 12 people.
The Taliban said they also carried out that hours-long attack on 19 August to mark the anniversary of Afghanistan's independence from the UK in 1919.
"Today at 13:00 (08:30 GMT) at Kabul's Abdul Haq roundabout a massive suicide attack on local and foreign intelligence facilities is ongoing," said a spokesman for the Islamist group of Tuesday's attack.
Nato's Secretary General Anders Fogh Rasmussen condemned the violence, saying it was an attempt to test Afghanistan's security transition (the handover of control from Nato to Afghan-led forces) that would not succeed.
"We have confidence in the Afghan authorities' ability to deal with this situation," said Mr Rasmussen in Brussels. "Transition is on track and it will continue."
It appears to be a complex operation with a number of suicide bombers involved, says the BBC's Quentin Sommerville in the Afghan capital.
Around five attackers are coordinating their operation from the high rise building which is under construction just 300m from the US embassy. Our correspondent saw a rocket-propelled grenade apparently overshoot the embassy.
US marines were seen on the roof of the embassy building assessing the situation and checking their defences were robust, he adds. Military helicopters are in the area.
Western security sources said Nato's International Security Assistance Force (Isaf) headquarters was also targeted, although an Isaf spokesman would not confirm the information. (BBC)