The Yemen government said it seized back the interim capital of Aden on Wednesday, a claim contested by the separatists who took control of the city and other parts of the south earlier this month.

The tussle between the pro-independence Southern Transitional Council (STC) and government troops comes nearly three weeks after the separatists took control of Aden, the government's base since Huthi rebels took over the northern capital Sanaa in 2014.

Information Minister of Yemen, Moammer al-Eryani tweeted that "The national army and security services have full control over the province's districts." And forces loyal to the internationally-recognized government of Yemeni President Abedrabbo Mansour Hadi were able to secure the presidential palace in Aden and the surrounding areas. 

However, a senior source in the Security Belt, a paramilitary force loyal to the STC, said the claims were unfounded.

"Our forces still control most of the districts in Aden," the source told AFP. "The government troops entered the outskirts of the city, but they were dealt with and pushed back."

AFP journalists saw separatist troops still patrolling the capital, near its international airport.

The clashes between the STC and government forces, who for years have fought alongside each other against the Iran-aligned Huthis, have raised concerns that the famine-threatened country could break apart entirely.

The separatists' seizure of Aden was seen as a major gain allowing the Security Belt to press on to take other strategic areas.

However, the Yemeni government drafted in reinforcements from the north and mounted a pushback on Wednesday.

An AFP correspondent in the east of the city witnessed shelling by advancing government forces fresh from their success in taking back control of Abyan province to the east on Wednesday.

A pro-government source told AFP fighting had erupted in the streets of Aden as loyalist troops fanned out there.

Abyan was the second southern province to be retaken by government forces in southern Yemen in the days following clashes with the Security Belt.

Earlier in the week, government forces also regained control of Shabwa province after beating back an attack by STC forces.

The new fighting comes despite repeated calls for a ceasefire by a Saudi-led coalition which intervened in the war in 2015 in support of the government after the Huthis seized the capital Sanaa and much of Yemen.

Since then, the conflict has killed tens of thousands of people, mostly civilians, in what the United Nations has described as the world's worst humanitarian crisis.

STC forces have also fought against the Huthis but want to see South Yemen regain the independence it gave up with unification in 1990. The separatists want to address what they say is a history of exploitation and marginalization of their people.

"We will sail together towards the safe harbour chosen by our people who have fought for this for so long," STC leader Aidarous al-Zoubeidi said in a speech on Tuesday.

The separatists have received support and training from the United Arab Emirates, even though it is a key pillar in the Saudi-led coalition backing the Yemeni government against the Huthi rebels.

The Yemeni government has repeatedly accused the UAE of "being responsible for the armed rebellion" in the south and urged it to stop backing "this militia."

Analysts say the break between Hadi's government and the separatists reflects a wider rift between Riyadh and Abu Dhabi.

But the UAE has rejected accusations it supported the separatists in their seizure of Aden and said it was "exerting all efforts to de-escalate the situation in Yemen."

In a joint statement this week, Saudi Arabia and the UAE called for cooperation with a coalition committee and for peace talks in the Saudi city of Jeddah.

(With input from AFP)