Syrian insurgents captured several government airmen after their helicopter crashed in a rebel-held area of northwestern Syria on Sunday, activists said.
The Idlib Media Center and the Britain-based Syrian Observatory for Human Rights said the helicopter went down near Jabal al-Zawiya, some 10 kilometers (6 miles) north of the town of Maarat al-Numan in Idlib province.
The aircraft experienced a technical malfunction and made an emergency crash-landing, according to the Observatory.
Syria's state news agency confirmed that a helicopter had crashed in Idlib after a mechanical problem and said the authorities were looking for the crew.
Observatory director Rami Abdurrahman said opposition fighters, including from the al-Qaida-affiliated Nusra Front, had taken four crew members prisoner.
Another airman survived the crash but was reportedly killed by his captors, and the fate of a suspected sixth airman is unknown, Abdurrahman said.
An amateur video posted online showed rebels inspecting the wreckage of the helicopter, which had rolled onto its side on a rocky hill. The aircraft's blue undercarriage was partially torn and the nose badly damaged.
Photographs posted by activists online showed the same crash site and at least two airmen in rebel custody.
The video and photographs appeared genuine and corresponded to other Associated Press reporting.
The Syrian military frequently uses helicopters to drop crude barrel bombs - giant canisters packed with hundreds of pounds of explosives and scrap metal - on rebel-held towns and neighborhoods.