Security sources and residents said clashes appeared to have spread to most of the city. The government urged the Saudi-led military coalition, which has been supporting Hadi against Iran-backed Huthi rebels who control much of the north, to intervene.
The southern separatists - who want the return of an independent state that ended with Yemen's unification in 1990 - backed Hadi's government against the Huthis but tensions between them had been rising. "A coup is ongoing here in Aden against legitimacy and the country's unity," Prime Minister Ahmed bin Dagher said in a statement.