Yemeni fighters of the southern separatist movement, which is loyal to exiled President Abed Rabbo Mansour Hadi, walk with the movement’s flag on a street in Aden’s Khormaksar district on July 15, 2015. (Saleh Al-Obeidi/AFP/Getty Images)

Yemeni militiamen allied with Saudi Arabia appeared Thursday to have driven Houthi rebels out of most of Aden, prompting members of the country’s exiled government to make their first visit in months to the southern port city.

The militiamen have made broad gains in the city since Tuesday, dealing a blow to the Houthis. The Shiite Muslim insurgents have besieged Aden for months.

The advances by the militiamen may give momentum to Saudi plans for reinstalling embattled Yemeni President Abed Rabbo Mansour Hadi. They also marked a rare tangible gain for a Saudi-led coalition that has conducted airstrikes for nearly four months but has failed to significantly drive back the rebel forces.

“Hadi delegated this group to return to Aden to work to prepare the security situation and ensure stability ahead of a revival of the institutions of state in Aden,” a local official told the Reuters news agency after the members of the exiled administration arrived by helicopter at a military air base.

The Houthis toppled Hadi’s government in February, triggering all-out war and forcing him to flee from the capital, Sanaa, to Aden. A month later, Hadi escaped to Saudi Arabia, and the Saudi-led coalition began airstrikes against the insurgents. Saudi Arabia, a Sunni powerhouse, views the Houthis as a proxy for its chief regional enemy, Shiite Iran.

On Thursday, Houthi forces in Aden faced a sudden assault by pro-Hadi militiamen, who may have received training in Saudi Arabia. Residents said later that the Houthis have withdrawn from most areas of the city.

Aden resident Saif Ali Hassan, 56, said the Houthis have all but lost control of the city. “They are surrounded in a few areas of the city, and they are getting hit hard by coalition airstrikes, which have helped the resistance fighters,” Hassan, a doctor, said by telephone.

During the assault, residents said, the militiamen used heavy weapons and armored personnel carriers. The fighters, from the Popular Resistance militia, captured Aden’s airport Tuesday and took the city’s main port a day later.

Houthi rebels, however, appear still to hold the presidential palace and other areas, residents said.

Mohammed al-Bukhaiti, a senior Houthi official in Sanaa, acknowledged the setbacks in Aden but said the rebels are fighting to recover ground lost in recent days.

“The claims of victory by the Saudi coalition are premature,” Bukhaiti said. “We are still engaged in heavy fighting.”

More than 3,500 people have been killed and 1.3 million displaced since March in fighting that the United Nations and aid agencies say has triggered a humanitarian disaster in the Arab world’s most impoverished nation.

Naylor reported from Beirut. Daniela Deane in Rome contributed to this report.

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