Afghan officials say they have detained or expelled several Afghan soldiers as part of a probe into the recent string of insider attacks.

At least 45 international troops have been killed this year after Afghan security forces turned their weapons on their coalition counterparts.

Afghan Defense Ministry spokesman General Zaher Azimi told reporters in Kabul Wednesday the Afghan military has taken steps to prevent such attacks and has so far arrested or expelled several “suspicious” army soldiers. Azimi did not give details.

His comments come just days after the U.S. military announced it was temporarily halting the training of 1,000 members of the Afghan Local Police in order to improve vetting procedures. NATO, which is responsible for training Afghan National Army and Afghan National Police recruits, has not suspended its training.

NATO says many of the so-called “green on blue” attacks are due to personal grievances and arguments, with about 25 percent attributed to Taliban infiltration, impersonation or coercion. Green on blue refers to a color coding system used by the military.

Separately, a suicide bombing killed 25 people in the eastern province of Nangarhar on Tuesday, in one of the deadliest attacks on civilians in recent weeks.

The attacker struck a funeral for a tribal elder in the remote Dur Baba district.

Officials say the district governor, Hamisha Gul, was the probable target. He was among the more than 50 people wounded in the blast. Police say the governor's son was killed.

There was no immediate claim of responsibility, but the Taliban is known to target Afghan government officials.

Both Afghan President Hamid Karzai and NATO condemned the attack.