SANAA, Yemen (AP) — Fierce fighting continued in southern Yemen between Emirati-backed separatists and the country’s internationally recognized government Thursday, security officials said, a blow to the Saudi-led coalition's declared ceasefire between the factions.

Battles in the flashpoint Abyan province between Saudi-backed government forces and Emirati-funded southern secessionists killed at least 54 fighters on both sides over the last 24 hours, said Yemeni security officials, who spoke on condition of anonymity because they weren’t authorized to brief the media.

The Saudi-led coalition, which is mired in a years-long conflict with Iranian-supported rebel Houthis, said earlier this week that the separatist and government forces had reached a truce. The agreement aims to close the rift between Saudi Arabia and the United Arab Emirates, powerful regional allies in the U.S.-backed Arab coalition against the Houthis.

Clashes in various provinces between the nominal allies in recent months had reopened a new front inside the larger civil war, complicating international efforts to broker a broader peace agreement.

The coalition deployed troops this week to observe the ceasefire in Zinjibar, the Abyan provincial capital. The monitors, who are shuttling between the two sides trying to establish a mechanism to restore the calm, expect to be deployed east of Zinjibar in the next few days, said security officials, even as each faction accuses the other of violating the truce.

The secessionist council, which is an umbrella group of heavily armed and well-financed militias propped up by the United Arab Emirates since 2015, hopes to restore an independent southern Yemen, which existed from 1967 until unification in 1990.

Saudi Arabia supports the internationally recognized government of President Abed Rabbo Mansour Hadi, who was driven into exile in 2015 when Houthi rebels seized the capital, Sanaa, and much of the country’s north. The ensuing war has killed over 112,000 people, according to the Armed Conflict Location & Event Data Project, and set off what the U.N. has labeled the world’s worst humanitarian crisis.

Also on Thursday, fighting erupted between government forces and Houthi troops amid a shaky U.N.-brokered truce around Yemen’s crucial port city of Hodeida, which is the country’s main gateway for international aid. Three civilians, including two children, were killed when mortar shells fired by the Houthis crashed into a southern residential neighborhood, according to witnesses and security officials. Three combatants also were killed in the exchange of artillery, they added.

The flare in violence comes as Yemen struggles to cope with a major coronavirus outbreak. Although testing remains limited, the number of people dying from COVID-19 symptoms has dramatically surged across the country.

Saudi Arabia announced a unilateral cease-fire earlier this year, citing the pandemic, but it quickly collapsed. The division in southern Yemen between the government and separatists has further hobbled health authorities' response to the virus in the Arab world's poorest country.