Gulf-backed forces loyal to Yemen's exiled government retook a fifth southern province on Saturday, extending recent territorial gains against Iran-backed rebels who control the capital.
The advance by the forces backing President Abd-rabbo Mansour Hadi has been aided by weapons and troops from Yemen's wealthy Gulf neighbours, as Saudi-led coalition warplanes continue to pound rebel positions.
The rebels "withdrew" and "handed over" Shabwa to the pro-government forces after they were promised a safe route out of the province, a military official told AFP.
Other army officials confirmed the rebel pull-out.
"The province was handed over" to the Southern Movement, a secessionist group whose militants have been fighting in loyalist ranks, said Salem al-Awlaqi, a political activist in Shabwa.
Military officials said this week that the pro-rebel governor of Shabwa -- which has substantial oil reserves -- had fled as loyalist forces prepared to enter the province.
They also accused the rebels of planting landmines in government buildings across Shabwa, as they had done in other provinces before fleeing.
Loyalist forces in the south launched an offensive last month against the rebels, forcing them out of main southern city Aden in mid-July.
They later advanced retaking the provinces Daleh, Lahj, and Abyan, in addition to Shabwa.
The advance is heading toward third city Taez, southwest of Sanaa. Analysts regard the city as the gateway to the capital, which the rebels overran last September.
After seizing Sanaa unopposed, the Houthis advanced on second city Aden in March, prompting intervention from a Saudi-led coalition aimed at restoring Hadi to power.
Renegade troops loyal to former president Ali Abdullah Saleh have joined the Houthis.
On the other side, the southern secessionists teamed up with pro-government troops as well as local Sunni tribes to form what they have dubbed Popular Resistance Committees.
Analysts say that the sweeping victories in the south are a result of the rebels pulling their forces back to Taez, where residents reported ongoing clashes.
Loyalist forces on Friday retook several facilities which had been held by the rebels in Taez, including police and civil defence headquarters, the government's Sabanew.net website reported.
In a telephone call, Hadi reassured the 35th Brigade commander in the city on Thursday that "Taez is on its way to being liberated and support will soon reach it."
Military sources say the coalition has provided Hadi's supporters with modern heavy equipment in recent weeks, including tanks and other armoured vehicles as well as personnel carriers and Yemeni soldiers trained in Saudi Arabia.
Six Emirati coalition soldiers have so far been reported killed in incidents linked to the Yemen operations.
Speaking from Abu Dhabi on Friday, Yemeni Foreign Minister Riad Yasin thanked the the UAE and Saudi for their support to his country.
The conflict has cost nearly 4,300 lives since March, half of them civilians, according to UN figures, while 80 percent of Yemen's 21 million people need aid and protection.
The five provinces so far retaken by pro-government troops, along with Mahra and Hadramawt, which the rebels never entered, comprise what was formerly known as the independent South Yemen.
It was its own state between the end of British colonial rule in 1967 and its union with the north in 1990.
A secession attempt four years later sparked a brief civil war that ended with northern forces occupying the region.