(Bloomberg) -- Yemeni government forces fought fierce battles with southern separatists in Aden on Wednesday after seizing a key checkpoint in the port city and retaking the capital of a neighboring province.

Local residents reported intense gunfire in Aden’s Al-Arish district as government fighters moved to seize the airport. Fighter jets from the Saudi Arabia-led coalition that supports the internationally-recognized administration were flying over the city, they said.

Clashes between government troops and the separatist Southern Transitional Council escalated this month in southern Yemen, fracturing forces meant to be united against Iranian-backed Houthi rebels, who come from the north.

The turmoil has raised questions over the strength of the Gulf Arab alliance that plays a crucial role in supporting the Trump administration’s policies against Iran. The STC is backed by the United Arab Emirates, a key member of the coalition.

The Gulf states have stressed their unity. Anwar Gargash, the U.A.E. state minister for foreign affairs, described ties with Riyadh as “existential.” Cooperation with the U.A.E. is “the cornerstone for security, stability and prosperity in the region in the face of extremism, chaos, discord and division,” Saudi Deputy Defense Minister Prince Khalid Bin Salman said on Twitter.

The two countries launched a military campaign in 2015 to restore the rule of President Abd Rabbuh Mansur Hadi and his government after the Iran-backed Houthis captured the capital, Sana’a. The conflict has killed thousands of people and caused one of the world’s worst humanitarian crises.

The Wall Street Journal reported on Tuesday that the U.S. administration is preparing to initiate direct talks with the Houthis, citing sources it didn’t identify.

To contact the reporter on this story: Mohammed Hatem in Dubai at mhatem1@bloomberg.net

To contact the editors responsible for this story: Riad Hamade at rhamade@bloomberg.net, Mark Williams, Michael Gunn

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