Ten Yemeni soldiers are feared dead after a helicopter crash in Saada, a Shia insurgent stronghold in the mountainous north of the country.
An unnamed official told Reuters news agency that the crash had been caused by a technical fault, adding: "The 10 soldiers are believed to be killed."
The government has fought Shia rebels in the region on and off since 2004.
Last week, a gun battle broke out between the two sides just hours after a ceasefire had been declared.
Houthi rebels from the minority Shia Zaidi sect in Saada have been battling the government intermittently for about six years.
More than 250,000 people have been displaced in the region because of the conflict.
The Yemeni government is also battling against southern separatists and militants sympathetic to al-Qaeda.