Saudi-backed forces loyal to Yemen's exiled government have seized a town south of the rebel-held capital, military officials said Tuesday, in their latest advance against Shiite Huthi rebels.

The "Popular Resistance Committees" -- comprising pro-government fighters, Sunni tribes, and southern separatists -- seized overnight the town of Utmah, about 100 kilometres (60 miles) south of Sanaa, the officials said.

The town is in the Shiite majority province of Dhammar next to Sanaa province, where the Iran-backed rebels have held the capital since September.

Loyalist forces also seized six towns in the mountainous central Ibb province, where local Sunni tribes have been clashing with the Huthis for months, the officials said.

Backed by a Saudi-led coalition that has been carrying out air strikes since March, pro-government forces have been battling for months to restore President Abedrabbo Mansour Hadi, in exile in Riyadh, to power.

The officials were unable to provide details on the number of loyalist or rebel casualties in the fighting.

Pro-government forces have launched a major counter-offensive in recent weeks and recaptured four southern provinces -- Abyan, Aden, Daleh, and Lahj.

The advance has been leading toward third city Taez, southwest of Sanaa.

Pro-government militia sources said clashes were ongoing in Taez, which would be a major prize if retaken by loyalist forces.

Elsewhere, military officials said the pro-rebel governor of the southeastern Shabwa province, Ali al-Awlaqi, fled to an unknown location on Monday as loyalist forces prepared to enter the province.

The officials accused the rebels of planting landmines in government buildings across the province, in a sign that they were planning to retreat.

Complaining of marginalisation, the Huthis descended from their northern stronghold last year and seized Sanaa unopposed.

They advanced on the main southern city of Aden in March, forcing Hadi to flee to Saudi Arabia and prompting Yemen's Sunni neighbour to lead an air war on the rebels.

As well as the Huthis, rebel forces include renegade troops still loyal to former president Ali Abdullah Saleh, who was ousted in 2012.

The latest turnaround in the fighting coincided with the appearance on the battleground of modern equipment that, according to military sources, the Saudi-led coalition had provided to Hadi's supporters.

A military source last week also reported the deployment of "hundreds of soldiers from Gulf countries" in the coalition to Aden, along with dozens of tanks and armoured vehicles.