Forces loyal to President Abedrabbo Mansour Hadi in Abyan province advanced towards Zinjibar and the neighbouring town of Jaar, the sources said.
Soldiers reached Al-Kud, five kilometres (three miles) south of Zinjibar where they clashed with Qaeda militants, while coalition Apache helicopters targeted extremist positions in the vicinity, according to the officials.
Twelve Al-Qaeda militants and three soldiers died in the fighting, a military official said.
Government forces last week expelled militants of the jihadist network's local branch -- Al-Qaeda in the Arabian Peninsula -- from Huta, the provincial capital of Lahj, as part of a widespread operation to secure southern provinces.
Coalition-backed forces have driven militants out of Aden, the southern city declared by Hadi as temporary capital after Shiite Huthi rebels stormed Sanaa in September 2014.
The Arab coalition launched a military operation in support of Hadi in March last year after rebels advanced on his refuge in Aden and forced him to flee to Riyadh.
But pro-Hadi forces managed over the summer to wrest back control of Aden and four other provinces thanks to the support of coalition firepower.
The coalition recently turned its attention to extremists, backing pro-government forces against AQAP and Islamic State group militants, who have taken advantage of the chaos to strengthen their grip on southern Yemen.
The operation comes as representatives of the government and the Iran-backed rebels continue with UN-sponsored peace talks in Kuwait, which began on Thursday.
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