Kabul , Afghanistan ( CNN ) -- Two Americans -- one a Green Beret -- were killed Monday when an assailant wearing an Afghan National Security Forces uniform opened fire on the group , U.S. and NATO 's International Security Assistance Force officials said . The shootout in eastern Afghanistan did n't last long , as coalition forces `` returned fire and killed the attacker , '' a U.S. official told CNN . Two Afghan army personnel also were killed , said Gen. Zahir Azimi , an Afghan Defense Ministry spokesman . A U.S. military official told CNN that at least 10 Americans were wounded as well . The assailant fired at the victims with a truck-mounted machine gun , Azimi said , after a meeting between coalition and Afghan forces at a military base in the Jalrez district of Wardak province , about an hour west of Kabul . Green Berets and Afghan forces are based there , a U.S. official said . A spokesman for the Taliban , the militant group that once ruled Afghanistan , said the shooter was an Afghan police officer , but it 's unclear if that was the case . A U.S. official said a variety of Afghan security forces -- including army , national police and perhaps local police -- were at a training-related meeting . The incident appeared to be the latest `` green-on-blue '' attack , or strike against coalition members by people dressed in police or army uniforms . Assailants conducting similar subterfuge killed dozens of coalition troops in 2012 . On Friday , a coalition contractor in eastern Afghanistan was killed when people wearing Afghan uniforms turned their weapons against ISAF members , NATO said . The last coalition soldier killed in a `` green-on-blue '' attack was a Briton , who was slain on January 7 . And in the last similar fatal assault on U.S. troops , two Americans were killed October 25 . The coalition has been working to thwart such insider attacks . Coalition soldiers are required to have a loaded weapon within reach at all times . In addition , the coalition ended training for hundreds of Afghan soldiers last year until the completion of background checks for insurgent links . Most of the insider attacks are believed to be the result of Afghan soldiers suffering from combat or emotional stress , a Defense Department official told CNN in September after an especially deadly weekend for coalition troops . Only about 15 % of the `` green-on-blue '' attacks are believed to be the result of insurgent links , and about 10 % come from infiltrators not affiliated with the military , the Defense Department official said . The latest attack comes a day after Afghan President Hamid Karzai outraged the ISAF commander by contending there are `` ongoing daily talks between Taliban , American and foreigners in Europe and in the Gulf states '' and `` that Taliban want longer presence of foreigners -- not their departure from Afghanistan . '' U.S. Marine Gen. Joseph Dunford , who oversees the NATO-led force , said that 's `` categorically false . '' `` We have fought too hard over the past 12 years . We have shed too much blood over the past 12 years . We have done too much to help the Afghan Security Forces grow over the last 12 years to ever think that violence or instability would be to our advantage , '' Dunford said . Newly installed U.S. Defense Secretary Chuck Hagel visited Afghanistan this weekend on his first overseas trip since his confirmation . Hagel told reporters he tried to reassure Karzai that the United States has no unilateral back-channel talks with the Taliban . Hagel , Karzai meet after strained Afghan weekend . `` Secretary Hagel addressed these questions directly with President Karzai in their meeting , '' White House spokesman Jay Carney said Monday . `` The last thing we would do is support any kind of violence , particularly involving innocent civilians . '' Carney noted that the United States and its coalition allies are staying the course with their stated policy to end the war that began in 2001 `` because we were attacked from Afghanistan . '' `` We 've drawn down the surge forces and we 're winding down our troop presence in Afghanistan , as we build up Afghan security forces and turn over security lead to Afghan security forces . And that progress continues , '' he said . Afghan police officer embraces suicide bomber to save others . U.S. general : No dangerous detainees to be released to Afghan custody . Journalist Masoud Popalzai reported from Kabul ; CNN 's Barbara Starr , Matt Smith , Wesley Bruer and Lindsey Knight contributed to this report , and Mark Morgenstein wrote it from Atlanta .
A Green Beret is one of two Americans killed in Afghanistan , a U.S. official says . Two Afghans also are killed ; 10 more Americans are wounded , coalition officials say . The assailant is dead , a U.S. official says . It was first fatal `` green-on-blue '' attack on coalition troops in two months .