KABUL: 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 Monday.

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. Spokesman Zabihullah Mujahid told AFP he was looking into what had happened.

The militia, which is leading a bloody, decade-long fight against Afghan government forces and the 140,000-strong foreign military, have used attackers with links inside the Afghan security forces to launch previous assaults.

Sundwall said it was the first attack of its kind “within collective memory” although Afghan soldiers have killed their American military trainers.On April 27, an Afghan ex-pilot opened fire after a row at a Kabul training centre, leaving eight US troops and an American contractor dead.

It was the worst attack of its kind and raised fresh questions over the massive US-led effort to expand and train Afghanistan's military and police to take control of security when foreign combat operations end in 2014.

Officials from NATO's US-led International Security Assistance Force (ISAF) say many “insider” attacks are committed by Afghans suffering from combat stress or following personal disagreements.

The high-security Ariana compound, the site of the latest incident, was used by the CIA, an Afghan government official told AFP on condition of anonymity.

The wounded American, whose injuries Sundwall said were “not life-threatening”, was evacuated to a military hospital in Afghanistan.The body of the dead American is expected to be returned to the United States shortly.

Sundwall declined to comment on whether the building was a CIA facility, while the CIA also refused to confirm it.

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

The previous attack targeting the US embassy and the neighbouring headquarters of the NATO-led International Security Assistance Force (ISAF) started on September 13 and lasted for 19 hours, leaving 14 Afghans dead.

At least six rocket-propelled grenades (RPGs) landed in the embassy compound in an attack which ambassador Ryan Crocker blamed on the Haqqani network. No US personnel were hurt.

The White House demanded Friday that Pakistan “break any link they have”with the Haqqanis, founded by Jalaluddin Haqqani, a warlord who was a CIA asset during the Soviet occupation of Afghanistan in the 1980s.

But Pakistan has responded by saying it will not launch an offensive against them, saying it is too busy fighting cross-border attacks from Afghanistan and local Pakistani militants.

In a previous strike against the CIA in Afghanistan, seven Americans were killed in a suicide attack on a CIA base in Khost, eastern Afghanistan, by a Jordanian triple agent in December 2009.