A NATO service member was killed in eastern Afghanistan on Thursday in an apparent “rogue” shooting by a man dressed as an Afghan policeman and another was killed elsewhere in the region by insurgents, the coalition said. The deaths brought to at least four the number of NATO troops killed in a bloody 24 hours in one of Afghanistan’s most volatile areas.

With violence flaring across the country since the first phase of a security transition began last month, an Afghan security official was also killed by a car bomb in the northeastern city of Kunduz, officials said.

In a brief statement, the NATO-led International Security Assistance Force said the latest killing of one of its troops came when “an individual wearing an Afghan National Police uniform turned his weapon against the service member.” It said ISAF and Afghan officials were investigating, but gave no other details.

Most of the NATO forces serving in the east, where a fractured and violent insurgency has developed over the past 18 months, are American, although there are also French troops in the area.

The killing of the ISAF member was the latest in a string of apparent rogue killings by Afghan police and soldiers or by insurgent infiltrators. Such killings have underscored the challenges as NATO scrambles to hand over security responsibility to Afghan forces across the country by the end of 2014. The first phase of that gradual process began last month.

In its statement, the coalition said another service member had been killed in a separate attack by insurgents in the east Thursday. No further details were available.

Late Wednesday, the coalition also said two of its troops had been killed by a roadside bomb. At least six ISAF troops have been killed in August, mirroring a steady, year-long trend of violence.

A total of 711 foreign troops were killed in 2010, the deadliest year of the war for the coalition, and at least 340 have been killed this year, according to independent monitor iCasualties.org and figures kept by Reuters.

U.S. and European military commanders have claimed significant success in the south in the past 18 months, mainly with the help of an additional 30,000 U.S. troops deployed in the Taliban’s southern heartland.

But the Taliban and other insurgents have shown an alarming ability to adapt their tactics and shift the focus of their attacks out of the south into the east and the once relatively peaceful north.

Thursday’s car bomb in Kunduz came two days after suicide attackers killed four security guards at a guesthouse in the city used by foreigners.

— Reuters