The move by the separatist Southern Transitional Council (STC) threatens to renew conflict between the STC and the Saudi-backed government, nominal allies under the coalition, even as the United Nations tries to secure a permanent nationwide ceasefire over the coronavirus pandemic. Yemen's internationally recognised government warned of 'catastrophic consequences' after the STC early on Sunday declared emergency rule in southern governorates including Aden, interim seat of the government that was ousted from power in the capital, Sanaa, by the Houthi movement in late 2014. 'The Coalition urges for an immediate end to any steps contrary to the Riyadh Agreement, and work rapidly toward its implementation,' the alliance said in a statement, referring to a power-sharing deal brokered by Saudi Arabia in November. It voiced support for the Saudi-backed government and said implementation of the deal would form a 'competent government' based in Aden to tackle the novel coronavirus, recent flooding and other economic and developmental challenges. Yemen has been mired in violence since the coalition intervened in March 2015 on Hadi's side. There has been military stalemate for years and the Houthis hold most big urban centres. The STC, which is backed by Riyadh's main coalition partner the United Arab Emirates, has long sought self-rule in the south and accuses Abd-Rabbu Mansour Hadi's government of mismanagement and corruption, a charge it denies. The UAE, which shares the STC's distrust of an Islamist party in Hadi's government, largely scaled down its presence in Yemen last year but maintains sway via southern fighters it backs. The Saudi-led coalition has announced a unilateral truce prompted by a U.N. plea to focus on the coronavirus pandemic. The Houthis have not accepted it and violence has continued. While Yemen has reported only one confirmed coronavirus case, aid groups fear a catastrophic outbreak should it spread among a malnourished population in a country with a shattered health system. The United Nations is trying to convene virtual talks on the truce, coordinated coronavirus efforts and confidence-building steps to restart negotiations to end the war that has killed more than 100,000.