The development raises concerns about the future of a Saudi-led coalition that has been fighting Yemen's Houthi rebels since 2015 and adds another complex layer to the civil war that has ravaged the Arab world's most impoverished country.
Infighting has raged for weeks between forces loyal to Yemen's internationally recognized government and the southern separatists, backed by the UAE — all ostensibly allies in the coalition.
Col. Mohamed al-Oban, a commander of the government's special forces in Abyan province, said the troops were on the road, headed from Abyan toward Aden on Thursday, when the strikes took place, killing at least 30.
He didn't say who was behind them, saying only the planes were from the Saudi-led coalition. The UAE also maintains warplanes as part of the coalition.
Officials in the UAE declined to immediately comment.
Yemen's foreign ministry tweeted a statement by Deputy Foreign Minister Mohammed Abdullah al-Hadrami, saying: "The government condemns the Emirati airstrike on government forces."
"We hold the UAE fully responsible for this explicit extra-judicial targeting" of the government forces, the statement said, adding that the airstrikes also left several civilians dead but without providing a specific death toll.
In the statement, the Yemeni government also urged the U.N. Security Council to condemn the attacks.
At least six raids were carried out by Emirati warplanes around the temporary capital, according to government military sources who asked to remain anonymous.
Yemen's civil war started in 2014 when Shiite Houthi rebels overran the capital, Sanaa, and much of the country's north. A Saudi-led coalition of mostly Arab states intervened a year later to try and restore President Mansour Abed Rabbo Hadi to power.
The UAE is part of that coalition but it never fully threw its support behind Hadi, allegedly over his ties to Yemen's Muslim Brotherhood, choosing instead to train and support the separatist militias.
Yemen was split into two countries, the North and South Yemen, during much of the Cold War before unifying in 1990 but a separatist movement has continued in the south. The Brotherhood is a pan-Arab Islamist movement that has been designated as a terrorist group by several Arab governments, including the UAE.
Though rare, Thursday's airstrikes were not the first time the Emirati planes struck government forces in Yemen, said Farea Al-Muslimi, a visiting researcher with London-based Chatham House.
In January 2018, an Apache helicopter belonging to the UAE hit two armored vehicles carrying government forces near the Aden airport during a similar bout of infighting between Hadi's government and the separatists.
However, this was the first time the government in an "explicit and irrevocable" statement turned against the UAE, heralding further fractures in the Saudi coalition, Al-Muslimi said.
Thursday's airstrikes also underscore the fragile nature of the Saudi-led coalition and could spell its doom, he added. "This is a natural ending for a coalition that actually never really existed," said Al-Muslimi. "It was based on instant goals and the belief the war in Yemen would be won quickly."
Thursday's airstrikes came a day after Yemeni government forces pushed into Aden to try and retake the city from the UAE-backed separatists.
Earlier on Wednesday, government troops wrested back control of Zinjibar, the capital of neighboring Abyan province, from the separatists and headed toward Aden.
Information Minister Moammar al-Iryani said Wednesday that government forces also reclaimed Aden's airport, the main hub for the country's south, but the separatists denied that.
According to officials speaking on condition of anonymity to discuss the matter with reporters, forces loyal to Hadi gained some ground at the Aden airport complex before the separatists forced them to retreat. Hadi's forces also lost Zinjibar again to separatists on Thursday.
Videos showing separatist militia in control of the airport were posted on social media on Thursday by the Southern Transitional Council, the separatists' commanding body.
The push by the government forces into Aden also underscored the seesaw nature of the fighting. Only weeks before, the separatists had gained much territory in southern Yemen, pushing government forces out of strategic cities and areas.