Beirut: Pictures provided by the Observatory showed groups of men gathering around a damaged helicopter lying on its side on a rocky hilltop.
Syrian state television confirmed that a military helicopter had crashed in Idlib, saying it was due to a technical failure and that search efforts to locate the crew were ongoing.
Abdel Rahman said two of the servicemen were being held by the Al-Nusra Front, while the other two were captured by an unknown Islamist group.
At least one more crew member was believed to be on the run, he said.
Regime helicopters are often used to drop crudely constructed barrel bombs on rebel-held areas.
Islamist rebels in Syria captured four crew members on Sunday when a regime helicopter crashed in the northwest province of Idlib, a monitor said, while a fifth serviceman was killed.
"A regime helicopter was forced to land in the region of Jabal al-Zawiya in the northwest, which is a bastion of (Al-Qaeda's Syrian affiliate) Al-Nusra Front," Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, told AFP.
"Four of the crew were captured and a fifth man was killed by armed men in a neighbouring village," he said.
Syrian state television confirmed that a military helicopter had crashed in Idlib, saying it was due to a technical failure and that search efforts to locate the crew were ongoing.
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At least one more crew member was believed to be on the run, he said.
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