ADEN, Yemen, Jan. 30 (Xinhua) -- Forces loyal to the separatist Southern Transitional Council (STC) made progress against the Saudi-backed Yemeni government and seized almost all areas in the province of Aden, a Yemeni official told Xinhua on Tuesday.
The Aden-based official said on condition of anonymity that the heaviest fighting took place overnight and ended in taking control over all military bases and banks of the government in the southern port city.
He said the STC forces rapidly advanced in the street fighting and imposed a tight besiege around the Presidential Palace in Aden's district Crater, where the government officials reside.
"Prime Minister Ahmed Obeid bin Daghr fled to a secure place under the protection of the Saudi-led coalition," a military source told Xinhua.
The anti-government forces approached from the main gate of the Presidential Palace and tried to storm it but Saudi soldiers intervened and protected the compound, the source said on condition of anonymity.
"After defeating the government forces in Aden and losing the battle, the prime minister may leave Aden via an airplane to Saudi Arabia," he added.
On Tuesday, the forces loyal to the STC declared victory and deployed around the government institutions and universities in Aden, raising flags of former South Yemen state.
The Interior Ministry sent an urgent appeal to the Saudi-led coalition, asking for its intervention to stop attacks by the STC forces.
Hours later, the Saudi-led coalition called on all armed groups to immediately stop clashes in Aden.
It is the second such call in a week by the coalition, which warned of necessary measures to restore security and stability in Aden, yet without specifying concrete steps or if military action would be taken in the temporary capital of Yemen.
However, sporadic fighting continued in Aden despite Saudi-led coalition's efforts to broker an agreement between the two warring rivals.
Witnesses told Xinhua that security forces loyal to the STC also surrounded and stormed the 4th Presidential Guard camp in the eastern part of Aden.
Hundreds of soldiers and senior officers allied with Yemen's internationally-backed President Abdu-Rabbu Mansour Hadi were arrested by the STC forces.
The infighting in Aden erupted on Sunday, following the end of a one-week deadline the southern leaders had set for the Saudi-backed government to resign, citing "rampant corruption and embezzlement."
The government, however, decided on Monday to ban demonstrations organized by the supporters of the STC and engaged in armed confrontations with other troops.
Yemeni President Hadi in Riyadh hold a meeting with his assistants on Monday night, describing the events in Aden as a "coup against the legitimacy."
According to Yemeni sources, Hadi urged all his forces "to confront any insurgency in Aden decisively and crush the separatist militias."
Tensions have recently started to spike between southern separatists and the government of Hadi over the control of the southern half of Yemen.
The southern port city of Aden is considered Yemen's temporary capital and the Saudi-backed Yemeni government has based itself there since 2015.
Yemen's government, allied with the Saudi-led Arab military coalition, has been battling Iran-backed Shiite Houthi rebels over the control of the country for about three years.
The coalition began a military air campaign in March 2015 to roll back Houthi gains and reinstate exiled Hadi and his government to the power.
The coalition also imposed air and sea blockade to prevent weapons from reaching Houthis, who are in control of most of the northern Yemeni provinces, including the capital Sanna.