Command officials say Afghan and coalition forces stationed in the area "are assessing the incident" but refused to disclose any further details about the shooting or the nationality of the slain soldier.
Thursday's attack was the second insider attack in the province in the past week.
On Sunday, three coalition troops were killed in Gardez. ISAF has yet to release an official casualty report identifying the soldiers who were killed.
Also dressed in an Afghan National Security Forces uniform, the shooter opened fire on the coalition troops, killing three before being killed by Afghan troops operating alongside allied forces.
Prior to that shooting, most recent insider attack against allied forces in Afghanistan took place in July at Kandahar airfield in the southern part of the country.
The shooter, a member of the Afghan National Army, fired on American and NATO soldiers based in Kandahar. Three U.S. troops were wounded in the exchange of gunfire.
The Afghan soldier survived the July attack and was taken into custody by ISAF and Afghan forces.
The threat of insider attacks by Afghan forces against U.S. troops continues to cloud local security transition efforts, as American commanders bring the 12-year Afghan War to a close.
Such attacks hit a deadly peak in later 2012, with more than 60 U.S. and coalition forces dying at the hands of their Afghan counterparts.
As a result, American military advisers have been banned from going into Afghan National Security Forces (ANSF) compounds unless it's for "direct mission planning," U.S. officers stationed in eastern Afghanistan told The Hill in July.
When American troops visit the ANSF compounds that typically ring the American combat outposts in Khost and elsewhere in the country, they must be armed, wearing full body armor and accompanied by a so-called "guardian angels" to provide security, according to U.S. advisers at Combat Outpost Sabari and Matun Hill.
When ANSF commanders and officers come to visit U.S. combat outposts, they are not allowed to carry weapons onto base, according to American military advisers here.
Despite the best efforts by American and NATO commanders to stem the rise in attacks by Afghan troops against coalition forces, there is no possible way to completely prevent the attacks from happening, according to chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey.
"We can dramatically lower the numbers [of attacks] ... but we can't prevent it," Dempsey said during a speech at the National Press Club in Washington late last year.