Nine people have been killed in fresh fighting in the city of Aden
The Saudi-led Arab coalition on Monday called for the Yemeni government battling southern separatists in the port city of Aden to hold talks on their demands, as fresh fighting killed nine people.
The coalition's spokesman, Colonel Turki al-Maliki, also urged "restraint" from the separatists and for them to "hold talks with the legitimate government".
"We are calling on the legitimate government to look into the demands of the political and social movement," Maliki said, referring to the separatists.
Aden has served as the headquarters of Saudi-backed President Abd Rabbo Mansour Hadi's government since it was forced out of the capital Sanaa by Houthi rebels three years ago.
The separatists - who want the return of the independent South Yemen that existed before 1990 - supported Hadi's forces against the rebels but tensions between the two sides have risen in recent months.
'We are calling on the legitimate government to look into the demands of the political and social movement'
- Colonel Turki al-Maliki, coalition spokesperson
The flare-up in Aden has added yet another dimension to one of the world's most complicated conflicts, a civil war that left thousands dead and millions on the brink of starvation.
On Monday, sporadic clashes continued after fighting overnight in the port city, especially in its north where separatist forces tried to take control of a military camp, security sources said.
The separatists dispatched additional forces from the central province of Marib and the southern province of Abyan, the sources said.
The forces from Abyan progressed towards Aden after clashes with loyalists on the way.
After the separatists seized government headquarters on Sunday, Prime Minister Ahmed bin Dagher denounced a "coup... in Aden against legitimacy and the country's unity".
He urged a Saudi-led military coalition backing Hadi to intervene in the government's defence.
The coalition launched air strikes against the Houthi rebels in March 2015 and sent troops to support Hadi's forces, fearing that Tehran would gain a foothold in the country on Saudi Arabia's southern border.
'Shooting' all night
On Sunday, security sources said pro-separatist units trained and backed by the United Arab Emirates had taken over the government headquarters in Aden after clashes.
By early evening, separatists took control of two roads leading to the presidential palace where several members of the government were staying, security sources said.
The International Committee of the Red Cross said fighting continued overnight in the port city.
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"All night shooting in Aden #Yemen, including heavy weapons," Alexandre Faite, the head of the ICRC delegation in the country based in Sanaa, said on Twitter.
"Those in the southern part of city, including (ICRC staff) still unable to get out."
UN envoy to Yemen, Ismail Ould Cheikh Ahmed, urged all parties to return to "calm and dialogue".
The top negotiator is to step down in April after three years of overseeing UN-brokered negotiations between the government and rebels, none of which have stemmed the violence in the country.
The US also urged calm in the southern city, saying that the fighting adds to the country's suffering.
"We call on all parties to refrain from escalation and further bloodshed," The US State Department said in a statement. "We also call for dialogue among all parties in Aden to reach a political solution."
Dagher held a cabinet meeting overnight to discuss "military developments and sabotage acts targeting government installations", loyalist news agency Saba reported.
He condemned the actions of "outlaws" against the "legitimacy represented by President Hadi" in the city.
Sunday's fighting in Aden killed 15 people including three civilians, hospital sources said, after separatist protesters were prevented from entering the city for a rally to demand the government's overthrow.
The separatists accused the prime minister of ordering his troops to open fire at the protesters.
Sunday's rally was called by the Southern Transitional Council, an autonomous body not recognised by the government and aimed at overseeing self-governance in southern provinces.
Former Aden governor Aidarous al-Zoubeidi formed the council in May last year after Hadi fired him.
The council had asked Hadi to make changes in the government and gave him one week to do so - a deadline that expired on Sunday.
It had warned that if Hadi did not accept the demand, its supporters would begin a protest campaign to oust Dagher's government.
South Yemen was independent - with former British colony Aden as its capital - from its formation in 1967 until 1990, when it was unified with North Yemen.