Aden: The Saudi Arabia-led coalition on Sunday launched an airstrike on a military site in Yemen's port city of Aden, a government official said.

"The Saudi-led airstrike was a warning message to the Southern Transitional Council (STC) forces that they must stop attacking government institutions in Aden," the official told Xinhua news agency.

The number of casualties was still unknown, he added.

The coalition confirmed in a statement that "an area that poses a direct threat to one of the important sites of the legitimate government was hit by an airstrike".

Following the airstrike, the STC forces, which had taken over the government's military bases and the presidential palace, announced its withdrawal on the Saudi-led coaition's request.

"Our forces started withdrawal after receiving an official invitation from Saudi Arabia to attend a dialogue session with the government," an STC source told Xinhua.

On Saturday, the coalition demanded an immediate ceasefire in Aden and warned of military step against violators, the Saudi Press Agency reported.

It ordered the military groups in Aden to withdraw from areas they occupied in recent days and keep away from government and private property.

The Saudi-backed Yemeni government accused the STC forces of staging a coup against the country's constitutional legitimacy with direct support from a regional power.

The Yemeni government held the STC and the United Arab Emirates (UAE), a key partner of Saudi-led coalition, full responsible for the consequences of the coup against the authorities in Aden.

It called on "the UAE to immediately and completely stop providing financial and military support to the rebel groups in Aden."

The southern port city of Aden is almost entirely under the control of the STC forces that are also allied to the Saudi Arabia-led coalition in the fighting against the Houthis.

Fighting in Aden started when senior leaders of the STC accused the Saudi-backed Yemeni government of "backing Islamists and leaking information to the Iran-backed Houthis" who targeted an army base in Aden last week, killing scores of soldiers including commanders.

Considered Yemen's temporary capital, Aden is where the Saudi-backed Yemeni government has based itself since 2015.

The impoverished Arab country has been locked in a civil war since late 2014, when the Houthis overran much of the country and seized all northern provinces including the capital Sanaa.