ADEN, Yemen, Aug. 10 (Xinhua) -- Forces loyal to the Southern Transitional Council (STC) on Saturday seized control over three military bases of the Saudi-backed Yemeni government following four days of clashes in the southern port city of Aden.

The STC's forces seized three bases of the presidential guard units tasked with protecting the headquarters of the country's cabinet in Aden after intense battles, according to a military official.

The presidential guard troops engaged in fierce armed confrontations with the STC forces but failed to repulse the latter's attacks that left around 15 people killed from both sides, the official said.

"Senior leaders and officers of the presidential guard forces fled Aden when the STC's forces stormed their locations," he added.

Witnesses told Xinhua that heavy forces of the STC backed by armored vehicles entered the government's army bases in Aden.

They confirmed that seven hours of intense clashes ended in capturing the government's military bases in Aden's neighborhood of Khormaksar as well as other government institutions in Aden.

Several armored vehicles, tanks and weapons caches belonging to the government were seized by the STC forces that were deployed in the area, according to the witnesses near the scene.

An army officer told Xinhua that warplanes of the Saudi Arabia-led coalition bombed reinforcements of extremists who were heading from neighboring Abyan province to fight against the STC forces.

"The Saudi-led airstrikes precisely struck the convoy composed of terrorist and Islamist elements who were heading to fight the STC forces that played a role in combating terrorism," the officer said on condition of anonymity.

Elsewhere in Aden, armed confrontations are still ongoing between the two warring rivals around the Presidential Palace in Crater neighborhood.

The STC's forces intensified the armed attacks against the well-guarded palace as the government forces refused to surrender or leave the area, according to local sources.

Explosions were heard in and around the densely populated neighborhood of Crater, where the last bastion of the Saudi-backed Yemeni government is located.

A number of the government's special security units surrendered to the STC's forces peacefully without armed confrontations and announced loyalty to the Aden-based southern council.

A source of Aden's local authority said that the STC's forces stormed the residential building of the country's Interior Minister Ahmed Maisry who fled using an armored vehicle towards the headquarters of the Saudi-led coalition forces in Aden.

The 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 the dialogue to resolve differences.

Considered as 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 Houthi rebels overran much of the country and seized all northern provinces, including the capital Sanaa.