Al-Qaeda fighters have retreated from an oil-rich southern province of war-ravaged Yemen in the face of an assault by an elite US-backed government force, a military official said Monday.

Al-Qaeda in the Arabian Peninsula (AQAP), seen by the United States as the global network's most dangerous franchise, has exploited Yemen's war to expand its presence in the country's south.

But special forces, trained by the United Arab Emirates and backed by the United States, on Wednesday launched a "major operation" against the jihadists in Shabwa province.

The group staged a "tactical retreat" from the province with no major clashes, the senior military official said, requesting anonymity as he was not authorised to talk to the press.

The jihadists appear to have moved even further south into neighbouring Abyan province.

Residents of an Abyan town near the Shabwa border said they counted at least 45 cars carrying armed AQAP militants through their district.

The Shabwa operation was conducted "under the supervision of the UAE military and with the support of US military advisors who are not present in the field," another high-ranking officer said.

He said the troops were Yemenis who were "trained for months" by UAE forces in Mukalla, in the Hadramawt province further east.

Several hundred well-armed and well-equipped soldiers make up Yemen's "elite force" in Shabwa, the official added.

The province is home to several oil and gas fields, as well as Yemen's only gas terminal Belhaf which was operated by French group Total until the company withdrew in 2015.

The oil giant pulled out of Yemen as the conflict intensified and a Saudi-led Arab military alliance, including the UAE, intervened on the side of the UN-backed government against Shiite Huthi rebels.

AQAP's Shabwa stronghold has also been a focal point in a long-running American-led drone war which has intensified since President Donald Trump took office in January.

A US air raid on the province in June killed AQAP emir Abu Khattab al-Awlaqi, according to the Pentagon.

The province has been the site of AQAP attacks in recent months, with the Yemen government reporting seven soldiers killed there last week in a suicide attack on a new military outpost.

- US, UAE role -

The Pentagon on Thursday confirmed that the United States was helping Emirati and government forces battle AQAP in Shabwa.

The UAE said the operation was being "closely supported by a combined UAE and US enabling force".

Pentagon spokesman Navy Captain Jeff Davis said Friday that the operation involved "a very small number" of US forces on the ground whose main task was to help the flow of information.

The assault aimed to "degrade" AQAP's ability to coordinate terror attacks abroad, he said, adding that the US had conducted more than 80 strikes in Yemen since February 28.

Trump ordered a special forces raid on Yemen in his first month in office which ended in the deaths of a US Navy SEAL and several Yemeni civilians in Baida province, bordering Shabwa and Abyan.

More than 8,000 people have been killed in the Yemen war since Saudi Arabia and its allies intervened in 2015 to support the government against the rebels, who had seized the capital and swathes of the country's north.

Yemen also faces a deadly cholera outbreak and stands at the brink of famine.

The United Nations has called Yemen "the largest humanitarian crisis in the world".

Source: AFP