Forces of the Southern Transitional Council (STC) managed on Saturday to seize Yemen's presidential palace following four days of intense fighting in the southern port city of Aden, a security official told Xinhua.

The local official, who asked to remain anonymous, said that "heavy armed forces of the STC entered the presidential palace in Aden's neighborhood of Crater without armed confrontations and fully captured the area."

He said that "the STC forces imposed a tightened siege around the presidential palace and forced the government forces to surrender peacefully."

The source said that all the Presidential Guard troops tasked with securing the government withdrew from the areas surrounding the palace.

Intense fighting raged for days between the two warring rivals around the country's presidential palace.

The STC confirmed in a statement obtained by Xinhua that "the southern armed forces completely captured the presidential palace."

A source of the STC confirmed to Xinhua that "our southern forces allowed the officers of the Presidential Guard troops to leave the area after their surrender."

High-ranking officials including a number of ministers of Yemen's government were transported via a private plane from the southern port city of Aden to Saudi Arabia.

Earlier in the day, the STC forces stormed and seized all the military bases of the Saudi-backed Yemeni government following four days of intense battles.

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 Houthi rebels.

Aden's fighting 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.

The STC threatened "to seize the presidential palace and expel all the members of the Saudi-backed Yemeni government who are linked to Muslim Brotherhood parties."

The Saudi-backed Yemeni government issued a statement and held the STC fully responsible for destabilizing the situation in Aden and fomenting trouble in the southern regions.

On Wednesday, the UN Special Envoy to Yemen Martin Griffiths expressed deep concerns over a military escalation in Aden and called on the parties involved to abandon violence and engage in dialogue to resolve differences.

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 Houthis overran much of the country and seized all northern provinces, including the capital Sanaa.