The Saudi-led coalition battling rebels in Yemen denied a major ground force had landed Sunday after reports of the deployment of troops in main southern city Aden.

"I can assure you that no (coalition) forces disembarked on the ground in Aden today," coalition spokesman Brigadier General Ahmed Assiri told the Saudi Al-Ekhbariya news channel.

Speaking to the Doha-based Al-Jazeera news channel, he said that the coalition "cannot comment on future or ongoing operations" and that "all options are open".

"The coalition leadership will not spare any effort to support the resistance and achieve positive results on the ground," Assiri said.

Asked to comment on images of men wearing helmets and carrying sophisticated weapons in Aden, Assiri said: "It is not in the interest of the security of operations or the safety of those carrying them out to announce details."

The Saudi-led coalition has been conducting an air war against the Huthi rebels and their allies since March 26 but Sunday saw the first reported ground deployment inside the country.

A government official in Aden as well as coalition-backed militiamen in the port city told AFP that a "limited" number of Saudi-led ground troops had deployed in the city to support loyalist forces fighting rebels around the airport.