South Sudan's President Salva Kiir
South Sudan's president Salva KiirReuters

The south Sudanese capital of Juba has witnessed fresh gunfire a day after the government said it had foiled a coup attempt by sacked vice-president Riek Machar.

Firing of heavy weapons was reported near the presidential compound and military headquarters on the outskirts of the city.

Some witnesses claimed that tanks were on the streets.

President Salva Kiir imposed a night curfew on Juba following earlier skirmishes which he blamed on Machar.

The former vice-president was said to be untraceable amid reports of artillery fire near his residence.

The streets of Juba were deserted except for military vehicles. Communications across the city had been cut off and civilians were told to stay indoors. Nearly 13,000 people have sought shelter at UN buildings.

Juba airport was also closed.

"In response to the criminal acts committed by this disgruntled group and for the sake of the security and safety of our citizens I declare curfew in Juba has to be observed from 6pm to 6am with immediate effect until further notice," said Kiir.

"Security organs are hereby directed to allow the residents of Juba to go about doing their normal work and move freely during the daylight hours."

At least 12 people are believed to have been killed so far but the casualties are expected to be far heavier.