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:

Media Statement Issued By The Department of Correctional Services

6 August 2021

The Department of Correctional Services can confirm that Former President, Jacob Zuma, has today, 06 August 2021, been admitted to an outside hospital for medical observation. pic.twitter.com/LoviT4oCwW

— Ministry of Justice and Correctional Services 🇿🇦 (@Min_JCS) August 6, 2021

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.