Yemen has been split by a seven-year-old war pitting a fractious coalition led by Saudi Arabia against the Iran-aligned Houthi group. The Houthis largely hold the north and the internationally recognised government is based in the south.

Rivalries among Yemeni factions in the coalition resurfaced recently as southern forces backed by the United Arab Emirates expand their reach, imperiling a new presidential council and further complicating international efforts to end the conflict.

The separatist Southern Transitional Council (STC) deployment in Abyan, expanding its presence there, follows gains in neighbouring Shabwa by the UAE-backed Giants Brigade against rival factions including the Islah Party.

The STC, which has vied with the Saudi-backed government for control of the south, said in an infographic on Tuesday that its military campaign aimed to "cleanse Abyan of terrorist organisation", specifying Islamist al Qaeda militants, while further securing Aden and other southern governorates, as well as roads between southern governorates.

Abyan this year has seen several attacks on soldiers that authorities suspect were carried out by Al Qaeda in the Arabian Peninsula, which used the war between the Houthis and the coalition to enhance its influence.

The Saudi-led coalition intervened in Yemen in March 2015 after the Houthis ousted the government from the capital, Sanaa, in late 2014. The conflict has killed tens of thousands of people and pushed millions into hunger.

In April, the Political Leadership Council formed under Saudi auspices assumed the powers of the president-in-exile as Saudi Arabia sought to strengthen the anti-Houthi alliance amid intense international pressure to end the war.

Council head Rashad al-Alimi on Monday issued a notice, seen by Reuters, to STC leader and council member Aidarous al-Zubaidi saying all military operations should be halted until the implementation of a troop redeployment in the south stipulated under a power-sharing pact brokered by Riyadh in 2019.

Instability in the south complicates United Nations efforts for a permanent ceasefire to pave the way for political negotiations to end the war. A U.N.-mediated truce between the coalition and the Houthis has largely held since April.

(Reporting by Yemen team; writing by Ghaida Ghantous; editing by Mike Harrison and Mark Heinrich)