A US citizen has been shot dead by an Afghan employee in a baffling attack at an annex to the US embassy used by the CIA in Kabul, officials said yesterday.

The gunman was killed in the incident at the the Ariana Hotel compound late Sunday and another US citizen also wounded, the embassy said.

It was the latest eruption of violence to hit supposedly secure sites in Kabul after Afghan peace envoy Burhanuddin Rabbani was assassinated on September 20 and a 19-hour assault targeting the US embassy on September 13.

The attack comes as Washington steps up pressure on Islamabad to tackle the Haqqani network, a group linked to al-Qaeda and loyal to the Taliban, blamed for much of the violence in Kabul and whose leaders are based in Pakistan.

"There was a shooting incident at an annex of the US embassy in Kabul involving an Afghan employee who was killed," said US embassy spokesman Gavin Sundwall. "One US citizen was killed, one was wounded."

Sundwall said the Afghan employee had acted as "a lone gunman." "The motivation for the attack is still under investigation," he added.

There was no immediate claim of responsibility from the Taliban.