The Saudi-led coalition backing President Abd Rabbou Mansour Hadi against Shia Houthi rebels poured more reinforcements Thursday into central Yemen, where more than 30 people were killed, military sources and witnesses said.
The Iran-backed Shia rebels, for their part, claimed to have captured several Saudi soldiers, parading one of them on television.
Backed by coalition air strikes, pro-Hadi forces pressed an operation in central Yemen on the road towards the capital, seized by rebels last September.
Five civilians, including two women, were killed when a coalition raid targeting rebels in northern Sanaa hit three houses, witnesses said.
Safanews.net, controlled by the rebels, put the death toll at 10.
After rebels backed by renegade troops loyal to ousted president Ali Abdullah Saleh seized Sanaa a year ago, they pushed Hadi into exile in March after advancing on his refuge in the southern city of Aden.
Pro-Hadi fighters, backed by troops trained and armed by Saudi Arabia, ejected the rebels from Aden in July and have since recaptured four other southern provinces.
Loyalists are now set on gaining control of Marib province east of Sanaa, in their advance on the capital.
On Thursday morning, "military reinforcements were dispatched to the northern front, 60 kilometres (36 miles) from Marib" city, an officer with the 14th Mechanised Brigade told AFP.
They included "20 armoured vehicles, three tanks and two artillery pieces, along with hundreds of soldiers from the national army and the Arab coalition", he added.
On the Sirwah front, west of Marib, 18 rebels were killed in fighting with coalition-backed loyalist forces, military sources said.
Air raids killed 10 more rebels in the southern Shabwa province, the sources said.
On Wednesday night, air strikes targeted insurgent positions in the southwestern city of Taez, Yemen's third largest, which is partly controlled by rebels. They also hit Dhamar in central Yemen.
Rebel television Al-Masirah showed footage of a man dressed in military fatigues who identified himself as Sergeant Ibrahim Hakmi of a Saudi brigade based in the Jazan border area.
The man said he was being held along with an unspecified number of other Saudi soldiers, without saying when or where he was captured.
Riyadh has yet to comment on the claim.
Saudi Arabia's southwestern border region has been the scene of frequent clashes and cross-border shelling since Riyadh launched an air campaign against the rebels in support of Hadi.
Several thousand troops from the Arab coalition, notably from the United Arab Emirates, have been deployed in the country.
The UN says nearly 4,900 people have been killed and some 25,000 wounded in the conflict since late March, while 80 percent of Yemen's 26-million population are in desperate need of aid and more than a million people have been displaced.