"The 10 soldiers are believed to be killed," the official said, blaming the crash on a technical fault.

The helicopter went down at Kahlan mountain, east of the provincial capital Saada, scene of heavy fighting over the past six months between the rebels and the government forces before they reached a shaky truce on Thursday.

The cause of the crash was "technical," an official said without elaborating, only adding that the captain of the helicopter, Lt. Col. Sadek Al-Junaid, was among the dead.

Yemen’s military said on Sunday that the truce was holding in the north and that joint commissions representing the government and the rebels had been meeting to implement the cease-fire.

The rebels said several roads had been reopened around their stronghold of Saada, while a two-week-old siege had been lifted of the army's encircled 103 Regiment.

But rebel sources said an exchange of prisoners has run into last-minute complications. "The authorities want us to release all the prisoners, which was not the agreement," one of them said.

The cease-fire is the government's latest bid in a campaign to crush a rebellion that began in 2004, killing thousands and leaving 250,000 homeless in recurring fighting.

The latest round of clashes erupted on Aug. 11, when government forces launched "Operation Scorched Earth" — an all-out offensive.

The six-point truce requires the rebels to reopen three major routes in the first stage: The road between Saada, Harf Sufian and the capital, Sanaa; the road from Saada west to Malahidh and the road from Saada east to Al-Jawf.

It also calls for a rebel withdrawal from government buildings, the return of arms seized from security forces, release of all prisoners including Saudis, handover of captured army posts, and a pledge not to attack Saudi Arabia.