Afghan authorities say gunmen have killed two local government officials in separate attacks in the country's south.

Officials say two assailants on a motorcycle shot and killed a prosecutor for the Gereshk district of Helmand province as he traveled to work on Sunday. Afghan security forces were searching for the gunmen, who fled the scene. In another incident, gunmen killed an agriculture department officer in the neighboring province of Kandahar.

No one claimed responsibility for the killings, but Taliban militants recently have intensified assassinations of Afghan officials they accuse of collaborating with U.S.-led NATO forces in the country.

NATO says coalition and Afghan troops killed four insurgents in security operations on Saturday. It says two insurgents were killed in the southwestern province of Wardak and two others were killed in eastern Afghanistan's Paktiya province.

The coalition also says a drone crashed on a routine patrol late Saturday in Jalalabad city in the eastern province of Nangarhar, causing no casualties. Witnesses say two houses were damaged in the crash. The Taliban says it shot down the unmanned aircraft, but NATO says it appears mechanical failure was to blame.