The shooting Sunday evening is the most recent in a growing number of attacks this year by Afghans working with the country's international allies. Some assailants have turned out to be Taliban sleeper agents, while others have been motivated by personal grievances.
Gunfire was first heard sometime after 8 p.m. local time around the former Ariana Hotel, a building that ex-U.S. intelligence officials said is the CIA station in Kabul. The spy agency occupied the heavily secured building just blocks from the Afghan presidential palace in late 2001 after the U.S.-led invasion that toppled the Taliban.
The U.S. Embassy said an Afghan employee of the complex shot dead an American citizen and wounded another before being killed.
"The motivation for the attack is still under investigation," the embassy said in a statement.
Embassy spokesman Gavin Sundwall declined to comment on what the targeted annex was used for, citing security reasons. Sundwall said the Afghan employee was not authorized to carry a weapon, and it was not clear how the man was able to get a gun into the secured compound.
The embassy did not provide information on the American was killed, and said the person wounded in the shooting was taken to a military hospital with injuries that were not life-threatening. It said the embassy has "resumed business operations."
The attack came less than two weeks after militants fired rocket-propelled grenades and assault rifles at the U.S. Embassy, NATO headquarters and other buildings in Kabul, killing seven Afghans. No embassy or NATO staff members were hurt in the 20-hour assault. But it plunged U.S.-Pakistan relations to new lows as U.S. officials accused Pakistan's Inter-Services Intelligence agency of supporting insurgents in planning and executing the Sept. 13 attack.
Sunday's assault also follows closely on last week's assassination of former Afghan President Burhanuddin Rabbani, who was leading a government effort to broker peace with the Taliban. He was killed when an insurgent who had claimed to be a peace emissary exploded a bomb hidden in his turban upon meeting Rabbani.
President Hamid Karzai called Rabbani's death a "big loss" and said greater security measures should be taken to protect top Afghan figures, including religious clerics and tribal leaders. A government spokesman said that the man who brought the suicide bomber to Kabul has been arrested.
NATO bases and embassies have ramped up security following a number of attacks over the past year by Afghan security forces against their counterparts. Since March 2009, the coalition has recorded at least 20 incidents where a member of the Afghan security forces or someone wearing a uniform used by them killed coalition forces. Thirty-six coalition troops have died. It is not known how many of the 282,000 members of the Afghan security forces were killed.
In December 2009, an al-Qaida double agent blew himself up at a CIA base in eastern Khost province, killing seven CIA employees. The attacker, a Jordanian man named Humam al-Balawi, had been brought into the base because he had claimed to be able to reach high-level al-Qaida leaders.
Meanwhile, political tension between Afghanistan and Pakistan continued to mount Monday as the Afghan Foreign Ministry warned Pakistan that if artillery attacks in eastern Afghanistan continue will harm relations between the countries.
The Afghan government has said that an unknown number of Afghan civilians have been killed by the shelling coming from Pakistani territory in recent days. The attacks have allegedly destroyed several houses and mosques and displaced hundreds of people from their homes.
The Foreign Ministry quoted Mohammad Sadeq, Pakistan's ambassador in Kabul, as saying that the attacks were not intentional and that he regretted the killings and the destruction of property. The Pakistani Embassy in Kabul could not immediately confirm the statement.
The Afghan censure comes as U.S. officials have sharpened their missives to Pakistan over the past week and half, drawing more direct lines between the government and the Haqqani network, which is affiliated with the Taliban and al-Qaida and is often blamed for attacks in Kabul.
NATO said Monday that its operations in the east in the past four months have killed more than 450 enemy fighters but that it is clear that the Haqqanis, who control large areas in the east, are still operating out of Pakistan.
"We have no credible intelligence indicating that the Haqqani network has eliminated their operating safehavens in Pakistan," said Brigadier Gen, Carsten Jacobson, a spokesman for NATO forces in Afghanistan. "They continue to plan and execute operations from across the border."
In the south on Monday, a NATO service member was killed in a bomb attack, making a total of 38 international troopers killed so far this month.