A United States citizen has been shot dead by an Afghan employee at an annex to the US embassy in Kabul used by the Central Intelligence Agency, officials said Monday.

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

It was the latest eruption of violence to hit supposedly secure sites in Kabul after last week's assassination of Afghan peace envoy Burhanuddin Rabbani and a 19-hour assault targeting the US embassy earlier this month.

The US is stepping up pressure on Pakistan to tackle the Haqqani network, a group allied with the Taliban which is blamed for much of the violence in the Afghan capital.

"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 carried out the shooting and that he 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. Spokesman Zabihullah Mujahid said when contacted by AFP Monday that he was looking into what had happened.

The insurgents, who are leading a bloody, decade-long fight against foreign and Afghan government forces, have used attackers with links inside the Afghan security forces to launch previous assaults.

An attack in May which killed six people at a Kabul military hospital is thought to have planned with assistance from inside the Afghan security forces.

Officials from the NATO-led International Security Assistance Force (ISAF) say that many "insider" attacks are committed by Afghans suffering from combat stress or following personal disagreements.

The incident took place late Sunday inside the Ariana Hotel compound, an annex to the US embassy.

An Afghan government official speaking anonymously to AFP said the Ariana compound was used by the CIA.

The injured US citizen, whose injuries Sundwall said were "not life-threatening", was evacuated to a military hospital in Afghanistan for treatment.

The body of the dead American is expected to be returned to the United States soon.

Sundwall declined to comment on whether the building was a CIA facility.

"I'm sure there will be an investigation. We take our security very seriously and it is under constant review," he said.

In December 2009, seven Americans were killed in a suicide attack on a CIA base in Khost, eastern Afghanistan, carried out by a Jordanian triple agent.