The emergence of a mysterious new pro-government Arab force in the Yemeni port city of Aden is fueling speculation that ground troops from the Saudi Arabia-led coalition have been deployed to combat the Iran-backed Shiite rebels and their allies, according to some news outlets.

Saudi Arabia, however, denied sending coalition ground troops into Yemen, report the Los Angeles Times and Al Jazeera.

The new armed unit is believed to be made up of up to 50 fighters including special forces operatives.

“There are no foreign forces in Aden, but the coalition continues to help fight against the Houthi militia,” Brig. Gen. Ahmed Asiri, a spokesman for the Saudi-led Sunni coalition, reportedly said in a statement Sunday.

Ali al-Ahmadi, a spokesman for the pro-government committees in Aden, echoed the spokesman’s denial, indicating that the forces fighting the rebels around Aden are Yemenis, not from the Saudi coalition.

Peter Salisbury, a Yemen-based analyst and journalist, reportedly said that he had been told members of the new fighting unit “are Yemeni but they have been trained abroad and will coordinate more closely with the coalition.”

“The local fighters don’t have access to the kind of weapons they have been seen with,” noted Al Jazeera’s Mohamed Vall, reporting from Saudi Arabia.

Meanwhile, Ali Bukhaity, a Yemeni political analyst, reportedly suggested on his Facebook page that the Arab forces were made up of  “at least three [Arab] nationalities.”

“We are going to witness a new chapter in the wars in Yemen,” he told the Times. 

Saudi Arabia has declined to comment specifically on the presence of Arab special forces in Aden, notes Al Jazeera. It has not completely ruled out the use of ground forces.

The presence of Saudi coalition ground troops in Yemen would mark a major escalation in the conflict.

Saudi-led airstrikes, assisted by U.S. logistical support and intelligence, have been targeting Houthis in Yemen since March 26.

The Houthis have joined forces with armed units loyal to former Yemeni President Ali Abdullah Saleh. Together, they are fighting armed groups on the ground who support Yemen’s internationally recognized President Abdu Rabu Mansour Hadi.

“The new fighting unit in Aden joined members of what is known as the Southern Resistance Committees, an anti-Houthi armed group, the resistance faction said,” reports the LA Times. 

Ahmadi, the spokesman of the anti-Houthi committees, told the Times that new force was “engaged in the fights and confrontations in areas near and around Aden airport” against troops loyal to Saleh.

According to the United Nations (U.N.), the fighting in Yemen since the Saudi-led bombings started has killed more than 1,000 people, including nearly 551 civilians.

Among the dead civilians are at least 115 children, the U.N.’s children agency UNICEF said.