Aden (AFP) - Iran-backed rebels in Yemen have blown up several bridges in the mountainous southwestern Taez province to hamper the advance of pro-government forces, military sources said Tuesday.

Government forces backed by air and ground support from a Saudi-led coalition launched an all-out offensive last week to push the rebels out of Taez and break the siege of loyalists in its provincial capital.

Taez is seen as crucial for the recapture of other central provinces and for opening the way to the rebel-controlled capital Sanaa farther north.

It is also important for securing the south, where loyalists have retaken five provinces since July, including Aden, seat of the provisional government of President Abedrabbo Mansour Hadi.

The Shiite Huthi rebels on Monday "blew up several bridges leading to Rahida to prevent the advance" of loyalist forces, said one of the sources in a reference to the province's second-largest city.

Military officials said this week that landmines planted by the rebels have already been hampering the progress of government forces and had caused casualties.

Loyalist forces are now stationed 12 kilometres (seven miles) away from Rahida after they regained several positions in clashes that lasted until early Tuesday and left five rebels and two pro-government fighters dead, according to the military sources.

Elsewhere, the rebels said they repelled a loyalist advance in Dhubab region on the Red Sea, killing 20 and wounding another 20, a toll that could not be independently confirmed.

In the neighbouring Lahj province, farther south, Hadi visited Al-Anad airbase, where Yemeni and coalition commanders are deployed to supervise the Taez offensive, a presidency source said.

"The visit is to oversee the military preparations to liberate Taez," the source told AFP.

Hadi returned from exile in Saudi Arabia on November 18, two days after the offensive to retake Taez began.

A key member of the coalition, the United Arab Emirates, said Tuesday that one of its soldiers in Yemen died of his injuries from a September 4 missile attack in Marib, east of the capital Sanaa.

His death in Germany, where he was hospitalised, raised to 64 the number of Emirati soldiers killed in the attack.

The United Nations says a total of more than 5,700 people have been killed in Yemen since the Saudi-led intervention began in March, nearly half of them civilians.