ADEN, Jan 28: Yemen's Prime Minister Ahmed bin Dagher on Sunday accused southern separatists of attempting a coup in the interim capital of Aden after they took over the government headquarters, report agencies.
The premier called on the Saudi-led coalition fighting Iran-backed Huthi rebels to intervene after fierce clashes that left at least 15 people dead.
Three civilians were among those killed, medical sources in four hospitals in Aden said.
Fighting erupted early on Sunday between military units loyal to President Abedrabbo Mansour Hadi and security forces backing southern secessionists.
The southern separatists -- who want the return of an independent state that ended with Yemen's unification in 1990 -- had backed President Mansour Hadi's government against the Huthis but tensions between the two sides had been on the rise.
"A coup is ongoing here in Aden against legitimacy and the country's unity," Dagher said in a statement.
Security sources told AFP that pro-separatist units trained and backed by the United Arab Emirates had taken over the government headquarters in Aden after clashes.
The fighting erupted after separatist protestors were prevented from entering the city for a protest to demand the government's ouster from Aden, established as its interim base after the Iran-backed Huthis seized control of the capital Sanaa in 2014.
An Associated Press journalist heard heavy gunfire in the Khor Maksar district, while thick black smoke rose in the sky after an airstrike. The fighting spread to other districts, including areas near the presidential palace.
Witnesses said residents were fleeing the area. Schools and universities were shut down and students were told to stay home.
Airport authorities ordered the evacuation of all planes, fearing that they could be damaged in the fighting. State-run Yemenia cancelled all flights to and from Aden.
The separatist Southern Transitional Council had planned a rally for Sunday to demand that the country's internationally recognised president, Abdrabu Mansur Hadi, sack his cabinet.
The council accuses prime minister Ahmed Bin Dagher and his ministers of corruption, and had given Mr Hadi a Sunday deadline to fire them.
Mr Hadi's government announced a ban on public gatherings on Saturday, as thousands of the Southern Transitional Council's supporters arrived in Aden ahead of the rally.
Members of the presidential guard had been deployed across the city early on Sunday to prevent the protests from taking place.
Mr Hadi's forces -- backed by a Saudi-led military coalition that includes the UAE -- are fighting Houthi rebels, who control large parts of the north of the country. The southern separatists want to secede from northern Yemen.
Although Hadi remains in exile in Saudi Arabia, his administration nominally controls about four-fifths of Yemen's territory, but political and military leaders in Aden now want to revive the former independent state of South Yemen.