Southern separatists say they withdrew from talks over a Saudi-sponsored power-sharing deal with the government due to ongoing military escalation in flashpoint province of Abyan.
Fighting has resumed in southern Yemen between Emirati-backed separatists and the internationally recognised government.
The secessionist Southern Transitional Council, an umbrella group of militias backed by the UAE, said late on Tuesday it informed Saudi Arabia of the suspension, accusing the government of Yemeni President Abdrabbuh Mansour Hadi of mobilising forces in the southern province of Abyan.
There was no immediate comment from Saudi-backed Hadi's government, and a spokesman for the Saudi-led coalition embroiled in a years-long conflict in Yemen was not available for comment.
The renewed violence comes after the separatists suspended participation in talks to implement a Saudi-brokered peace deal.
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Challenge to Saudi efforts
The separatists' announcement could thwart Saudi efforts to close a year-long rift amid a broader war against Iran-backed Houthi rebels.
Government forces allegedly have killed more than 75 separatist fighters in the flashpoint province of Abyan since June 22, when the two sides agreed to a ceasefire after months of infighting, the STC said.
The secessionist group also accused the government of not paying salaries and pensions in the southern provinces, particularly for military and security personnel.
Hours after the announcement, fighting resumed overnight between the separatists and government forces in Abyan, where the Saudi-led coalition deployed troops in June to observe the ceasefire, officials from both sides said.
They spoke on condition of anonymity because they were not authorised to speak to reporters.
UAE, Saudi divergence
The secessionist council, comprised of heavily armed and well-financed militias propped up by the UAE since 2015, hopes to restore an independent southern Yemen, which existed from 1967 until unification in 1990.
The group declared self-rule over the key port city Aden and other southern provinces in April before it abandoned its aspirations for self-rule late in July to implement the stalled peace agreement with Hadi's government.
The power-sharing deal, signed in the Saudi capital of Riyadh last fall, sets the stage to end a long-running rivalry between the two sides. The agreement was never implemented.
Saudi Arabia last month proposed a plan to "accelerate" the deal’s implementation, which calls for the creation of a new government within 30 days and the appointment of a new governor and security director for Aden.
Tuesday's development likely would abort these efforts and reopen a new front within the broader Yemeni conflict.
It came as Yemen struggles to cope with a major coronavirus outbreak and heavy rains and flooding that recently engulfed several parts of the Arab world's poorest country.
The United Nations said on Tuesday that some 150 people died in the flooding and about 300,000 people lost their homes and livelihoods.
World's worst humanitarian crisis
UN spokesman Stephane Dujarric warned that humanitarian groups were running low on emergency shelter and other non-food items in several districts.
Dujarric said the UN humanitarian response plan "is only 24 percent funded," and he urged donors to pay all outstanding pledges.
Donor countries recently cut back on aid to Yemen amid the coronavirus pandemic and also due to concerns that the aid might not be reaching intended recipients in territories controlled by the Houthis.
The Yemeni government has reported on a little more than 1,900 confirmed virus cases, including 557 deaths in areas under its control.
The Houthis reported only three confirmed cases and one fatality, and have not reported cases for over four months.
The number of people dying from symptoms of Covid-19 –– the illness caused by the virus –– however, has dramatically surged across the country.
Yemen's descent into turmoil started in 2014 when Iranian-backed Houthi rebels overran the capital, Sanaa, and much of the country's north, driving Hadi's government into exile.
The Saudi-led coalition, which is backed by the US, intervened the following year to try and restore Hadi's rule.
The stalemated war has killed over 112,000 people and ignited what the United Nations has labelled the world's worst humanitarian crisis.