A bomb-laden vehicle exploded Sunday killing seven soldiers in south Yemen, where government forces backed by air power from an Arab coalition have launched an offensive against Al-Qaeda, military sources said.
In the southeast, pro-government forces regained an airport and other areas on the outskirts of the city of Mukalla, which had been under Al-Qaeda control since April last year, similar sources said.
The bombing, which also wounded 14 soldiers, targeted an army convoy as it entered militant stronghold Zinjibar, capital of Abyan province, said the sources, blaming Al-Qaeda for the attack.
Forces loyal to President Abd-rabbo Mansour Hadi began the Zinjibar offensive on Saturday, after similar assaults pushed the militants from other areas in the south.
The Saudi-led coalition that has been battling Iran-backed rebels across Yemen since March 2015 has deployed Apache helicopters to support loyalists fighting on ground.
Pro-Hadi forces "retreated from Zinjibar after they entered on Saturday night" from the city's southern gate, an officer in Abyan told AFP.
"The withdrawal was decided following information that Al-Qaeda was preparing other car-bomb attacks against our troops," added the officer who requested anonymity.
Government forces also launched an offensive Saturday to drive the militants from the neighbouring town of Jaar.
Fighting there killed 25 Al-Qaeda fighters and four soldiers as loyalists seized Al-Kud, five kilometres (three miles) south of Zinjibar, military and medical sources said.
"After our withdrawal, Apache helicopters will target Al-Qaeda positions to secure the town," said another officer, adding that helicopters had foiled two attempts to attack troops using vehicle bombs in Al-Kud.
Meanwhile, the Arab coalition carried out a series of air raids against Al-Qaeda in Mukalla, military sources said.
Residents reported heavy explosions as coalition jets struck Al-Qaeda-held arms depots in the city.
"The air raids are in preparation for a ground operation as part of a major military offensive to chase Al-Qaeda out of Mukalla and the entire Hadramawt province," an officer said.
Later Sunday, Yemeni ground troops backed by coalition air power advanced on the eastern outskirts of Mukalla, where they seized Riyan airport and an army brigade headquarters Al-Qaeda had held for the past year, military sources said.
Coalition-backed forces have driven militants from Aden, the southern city declared by Hadi as Yemen's temporary capital after the Shiite Huthi rebels overran Sanaa in September 2014.
And last week, government forces expelled militants of the militant network's local branch -- Al-Qaeda in the Arabian Peninsula -- from Huta, the provincial capital of Lahj.
The latest fighting comes as representatives of the government and the Iran-backed rebels continue UN-sponsored peace talks in Kuwait.
The negotiations, which began on Thursday, are under pressure to firm up a fragile ceasefire that went into effect on April 11, and from which the militants are excluded.