Mark Dummett, BBC News, Kabul
I'm in a basement in the heart of the city surrounded by key government buildings, the presidential palace and various ministries.

About an hour ago we heard the first series of explosions. Since then we have heard the sound of gun battles on the street outside. We haven't been able to speak to anybody in government as phone lines are down.

I have been told by security here that there is a gun battle and that there are at least two groups of attackers. Some were firing from the fourth floor of a building around here. Other attackers have detonated bombs.

We are not entirely sure what the scene is outside - but we think there was a series of bomb attacks followed by this fighting as the army and police try to clear the rest of the attackers.

A statement on a Taliban website said the attack had specifically targeted government buildings and the hotel.

There are reports of one recent massive explosion in the diplomatic quarter.

Nato has said international troops are helping Afghan forces secure the area.

Streets in the centre of the city have been closed and hotels and government buildings have been locked down.

A spokesman for the interior ministry has told the BBC that several insurgents had entered a private building - possibly a shopping centre - which was the focus of the gun battle with Afghan security forces.

One official trapped in a government building told the Reuters news agency: "It is a chaotic scene, we do not know what to do and where to go."