Forces loyal to Yemen's government have re-entered the southern city of Aden, which they lost to previously allied separatists earlier this month.
Information Minister Moammar al-Eryani said troops and militiamen had taken full control of the city after securing the airport and presidential palace.
But a separatist militia commander said it was still in control of most areas.
The fighting has exposed a rift within the Saudi-led coalition supporting the government in Yemen's civil war.
Saudi Arabia backs President Abdrabbuh Mansour Hadi, while the United Arab Emirates backs the separatist Southern Transitional Council (STC), which accuses Mr Hadi's cabinet of mismanagement and is critical of his ties to Islamists.
For the past three years, the two sides have been part of an uneasy alliance against the rebel Houthi movement, which controls much of north-western Yemen.
The civil war has triggered the world's worst humanitarian disaster, with 80% of the population - more than 24 million people - requiring humanitarian assistance or protection, including 10 million who rely on food aid to survive.
Aden has served as the government's temporary capital since 2015, when President Hadi and his cabinet were forced to flee Sanaa by the Houthis.
Almost three weeks ago, after a separatist leader was killed in a Houthi attack, the STC-aligned Security Belt militia - which is armed and funded by the UAE - seized control of Aden from Saudi-backed forces after three days of fighting that left dozens of people dead.
The separatists also overran cities and towns elsewhere in the south, including Ataq, the capital of Shabwa province, and Zinjibar, the capital of Abyan province.
The STC demanded that Mr Hadi's cabinet be replaced, but the government said it would not negotiate until the separatist fighters withdrew from military installations and returned to their previous positions. It accused the UAE of responsibility for the "armed rebellion" - an allegation that officials in Abu Dhabi denied.
On Monday, two days after pro-government forces retook Ataq, the UAE and Saudi Arabia issued a joint statement calling for a ceasefire in the south and dialogue.
But the fighting continued and on Wednesday morning troops and pro-government militiamen reportedly pushed separatists out of Zinjibar.
On Wednesday afternoon, they retook Aden's airport before pushing into the city, according to Mr Eryani and local media.
Witnesses told Reuters news agency that clashes could be heard around the airport and in the central districts of Khormaskar and al-Arish.
Later, the minister tweeted that the presidential palace and its surroundings had been "secured" amid "great pubic satisfaction and welcome".
Soldiers & officers of the Presidential Protection Brigades secured the Maasheq Palace in #Aden and the surroundings. the National Army & the security forces impose full control over Aden districts amid great public satisfaction and welcome.— معمر الإرياني (@ERYANIM) August 28, 2019
He also said detained STC fighters had been pardoned and set free so that they could be redeployed elsewhere to "restore the state and defeat" the Houthis.
There was no immediate comment from the STC, but UAE-based Sky News Arabia cited Security Belt commander Wadah Omer Abdul Aziz as saying its fighters remained in control of most areas of the city.
Security officials meanwhile told the Associated Press that Security Belt fighters had not fled Aden and were still in their camps.