(CNN) -- A man in the uniform of an Afghan soldier shot and killed a member of the NATO-led International Security Assistance Force in eastern Afghanistan on Sunday, ISAF reported.
The killing, which was still under investigation Sunday afternoon, follows a long series of "insider" attacks by Afghan troops or infiltrators on U.S. and allied troops, including one in September that killed three Americans in eastern Afghanistan.
So-called "green on blue" attacks killed dozens of coalition troops in 2012, prompting the U.S. command in Kabul to stop some joint operations with Afghan security forces.
Sunday's attack came a day after U.S. Secretary of State John Kerry and Afghan President Hamid Karzai worked out what Kerry called "the major issues" in talks aimed at keeping some American military forces in Aghanistan after 2014. But a potential deal-breaker, legal immunity for U.S. troops, was referred to a council of Afghan elders.
In Iraq, the failure to agree on the immunity issue led to the withdrawal of all American troops at the end of 2011. Without an agreement on immunity, U.S. troops would leave Afghanistan with other NATO contingents at the end of 2014.