Former South Africa's President Jacob Zuma has been admitted to a hospital outside prison for medical observation, the prison authorities have said.

His foundation said it was an "annual medical routine check-up" and there was "no need to be alarmed".

As a former head of state Zuma is treated at a military facility, the authorities said.

The former president has been serving a 15-month prison sentence since 7 July for contempt of court.

Prison authorities say he's entitled to seek medical treatment like any other detained person.

The ministry of justice tweeted the full statement:

https://twitter.com/Min_JCS/status/1423520852633657344

Next week, the former president is scheduled to appear in person on a separate issue - an arms deal corruption case.

He has pleaded not guilty to involvement in the $5bn (£3bn) deal.