Kabul, Afghanistan (CNN) -- Five Afghan soldiers were accidentally killed early Thursday in a NATO airstrike in eastern Afghanistan, authorities said.
Eight other members of the Afghan National Army (ANA) were wounded in the strike in Charkh district of Logar province, Gen. Zahir Azimi, a spokesman for the Afghan Defense Ministry, said in an emailed statement.
NATO's International Security Assistance Force (ISAF) confirmed the deaths from one of its operations, describing them as an accident.
"An investigation is being conducted at this time to determine the circumstances that led to this unfortunate incident," ISAF said in a statement, expressing its condolences to the victims' families.
"We value the strong relationship with our Afghan partners, and we will determine what actions will be taken to ensure incidents like this do not happen again," the statement said.
The deaths come as NATO is preparing to withdraw the vast majority of its soldiers from Afghanistan by the end of the year.
U.S. President Barack Obama has warned his Afghan counterpart, Hamid Karzai, that the United States may pull out all of its troops if a new security deal isn't signed.
One of Karzai's brothers, Qayum, has withdrawn his candidacy for the presidency in elections scheduled for April, spokesman Mohammad Hamid Saboori said Thursday.
Qayum Karzai has endorsed former foreign minister Zalmai Rassoul for the elections, the spokesman said.
CNN's Mitra Mobasherat contributed to this report.