Dozens of people have been killed in clashes in northern Yemen between the army, their allied tribes and Houthi fighters, according to military and tribal sources.
The clashes intensified on Saturday in the city of Amran as Yemeni jets bombed rebel positions, sources told the AFP and Reuters news agency.
A medical official in Amran told AFP that "at least 40 people were killed" in the western areas of the city. Military and tribal sources told the agency that dozens were killed in other areas.
"Our hospital received 20 dead bodies, including soldiers, tribal fighters and rebels, and 60 wounded, some with serious injuries," an official at Amran's main hospital told AFP.
"The number of casualties is beyond our capacity," he said.
Houthis have been battling the central government for years from their northern Saada heartland, advancing from their mountain strongholds towards the capital Sanaa.
Clashes erupted anew last month in the north, ending an 11-day truce agreed after mediation backed by the UN envoy Jamal Benomar.
Al-Qaeda gunmen kill six soldiers
In a separate incident, suspected al-Qaeda gunmen ambushed and killed six soldiers in the southern province of Abyan, a military official said.
"Gunmen belonging to al-Qaeda have ambushed an army vehicle" on a main road outside Mahfad, shooting dead all of the soldiers on board, the official told AFP news agency on Sunday.
The attackers then took the soldiers' weapons and fled, the official added.
In late April, the Yemeni army launched a ground offensive against al-Qaeda in Abyan and nearby Shabwa province.
The operation aimed to expel fighters of al-Qaeda in the Arabian Peninsula from smaller towns and villages in the two provinces that escaped a previous sweep in 2012.
According to an AFP tally compiled from official and other sources, Yemeni security forces lost 374 personnel during the first half of 2014 fighting al-Qaeda, northern rebels and southern separatists.