Saudi Arabia denied it has deployed ground troops in Yemen after media reports said the Arab special forces were seen fighting the Houthi rebels in the port city of Aden. While Riyadh is heading the military coalition launching airstrikes in Yemen against the Shiite Houthi rebels, it has consistently refused to address reports about the presence of its ground troops in the embattled country.

Al Jazeera reported that dozens of Arab troops were seen arriving in Aden to defend the city against the Houthis and their allies, but a spokesman for the anti-Houthi Southern Popular Resistance told Reuters that the fighters were Yemeni nationals.

A Saudi spokesman also refuted the claims. "There are no foreign forces in Aden but coalition continues to help fight against the Houthi militia," Brigadier General Ahmed al-Asiri said, according to Al Jazeera.

The reports come shortly after the announcement of a “historic” unified Arab military force drawing on nations from the Gulf region. The move was prompted by the unprecedented regional threats posed by the Islamic State group and Iran’s proxies in Yemen, Iraq and Syria. Riyadh has not ruled out the possibility of a ground strike in the future, and previous reports indicated that the country was mobilizing ground troops as the strikes in Yemen began.

Aden is a stronghold of the anti-Houthi movement loyal to the internationally recognized President Abed Rabbo Mansour Hadi, who fled the country following a rebel attack in March. The Houthis control the capital Sanaa and large swathes of the country’s north, and are supported by militants loyal to former president Ali Abdullah Saleh.

The World Health Organization said in a recent report that the fighting has so far killed over 1,244 people, around half of whom are civilians, and 300,000 people are thought to have fled the country. U.N. Secretary General Ban Ki-moon voiced his concern about the fighting’s impact on the country’s populace. "There are credible reports of families in Aden trapped by the bombardment and snipers targeting civilians in the street," Ban said in a statement, according to BBC. Activists and rights groups have also accused the coalition of using cluster bombs in their attacks; Riyadh has reportedly denied these allegations.

The U.N. warned that Yemen’s infrastructure will soon collapse under the strain of the sustained fighting. "The services still available in the country in terms of health, water, food are quickly disappearing because fuel is no longer being brought into the country," Johannes van der Klaauw, a spokesman for the U.N., told Agence France-Presse. "If something is not done in the next few days in terms of bringing fuel and food into the country, Yemen is going to come to a complete stand-still."