Forces backed by the United Arab Emirates have taken over the airport in the southern city of Aden, according to Yemeni security officials, further fueling tension between internationally recognized President Abed Rabbo Mansour Hadi and the UAE.

The officials said that one soldier from among the forces guarding the airport died in clashes Wednesday morning. The officials spoke anonymously as they were not authorized to brief the media.

The UAE contributed forces to the Saudi-led coalition that secured Hadi’s return to the country following his exile in 2014. Hadi was originally forced to flee the capital, Sanaa, when it was seized by Shiite rebels, and Aden became his temporary seat of power.

However, tensions have grown between Hadi and the UAE over control of Aden’s airport, the main gateway to Yemen’s second largest city. UAE-led forces have made several previous unsuccessful attempts to seize the airport.

Hadi’s supporters accuse the UAE of aiding groups attempting to create an independent government in the south of Yemen, which would allow the leading economic power in the region to maintain a permanent presence in the south with its strategic ports.

Conflicts over the airport started in February when the head of airport security Saleh al-Emeiry, an ally of the UAE, refused to allow Hadi’s plane to land in Aden. Hadi ordered Emeiry fired and clashes broke out when armed Hadi loyalists arrived at the airport to enforce his decree. Since then control of the airport had remained split between UAE-backed forces and Hadi supporters.

In May, Hadi sacked two senior officials from the south who allegedly supported the separation and had ties to the UAE. The move was met with protests in the south and fueled further calls for separation.

Meanwhile, The United Nations envoy for Yemen said on Tuesday that the cholera outbreak in the war-ravaged country has killed over 500 people since the disease reemerged last month.

Ismael Ould Cheikh Ahmed said at a Security Council briefing that there are 60 thousand suspected cases of the cholera in its second outbreak in Yemen in six months.

The UN envoy said that Yemen’s collapsing medical sector contributed to the rapid outbreak, noting that less than 45 percent of medical facilities are functioning and only half of Yemenis have access to clean water.

The World Health Organization said in its latest update on Monday that the disease continues to spread but at a slower pace, putting the death toll at 471.

A Saudi-led coalition has been battling Shiite Houthi rebels in Yemen since March 2015, in a war that has killed more than 10,000 civilians.