Yemeni government forces have sent reinforcements to the Red Sea coast to drive Iran-backed rebels from a key global shipping route, military officials said on Saturday.

Houthi insurgents and their allies, forces loyal to former president Ali Abdullah Saleh, control most of the country's Red Sea coastline.

That includes Dhubab, just 30km from the strategic and busy Bab al-Mandab strait linking the Red Sea and the Indian Ocean.

Two US warships and an Emirati vessel in the Red Sea came under missile attack from rebel-held territory in September and October.

The government now aims to "push back the rebels away from the western coast and Bab al-Mandab, and to secure maritime navigation in the southern part of the Red Sea," a military official said.

Pro-government forces have been sent to the area, backed by tanks, other armoured vehicles and Katyusha rocket launchers, military officials said.

They said the offensive aimed to wrest back control of the coast from Dhubab as far north as al-Khukha 90km farther north.

Troops were also sent by the Saudi-led Arab coalition which intervened in March 2015 to prop up the government of President Abd Rabbuh Hadi.

Pro-government troops seized Dhubab in early October 2015, giving them effective control of Bab al-Mandab.

The rebels managed to recapture the area in February.

Hadi ordered the assault ahead of meeting UN special envoy Ismail Ould Cheikh Ahmed in southern port city and temporary capital Aden on Thursday.

Ould Cheikh Ahmed was there to discuss a new attempt to end the country's conflict.

The government-run sabanew.net website said Hadi handed him a letter reiterating the government's rejection of a roadmap the envoy presented in October, which would see the president eased out of power.

Hadi, who has spent most of his time in Riyadh since the conflict broke out, flew to Aden last Saturday on a surprise visit.

Thursday's meeting was his first with the UN envoy to take place in Aden.

Clashes raged on Friday in several areas in northern Yemen, along the border with Saudi Arabia, military officials said, as coalition warplanes pounded rebel positions.

Air strikes targeted rebels in Nahm, east of Sanaa, and in Ras Isa oil terminal on the Red Sea.

More than 7,000 people have been killed and nearly 37,000 wounded since the conflict escalated after the Saudi-led military coalition intervened in March 2015 to support Hadi.