Arnold Schwarzenegger has reassured fans after a video emerged showing him being drop-kicked in the back during an event in South Africa.

The Hollywood actor-turned-politician was recording a Snapchat video inside a gymnasium when someone attacked him from behind.

The attacker was quickly detained by security, organisers said.

Schwarzenegger, 71, the former governor of California, was in South Africa attending the Arnold Classic Africa sporting event.

The attack happened at the Sandton Convention Centre in Johannesburg, according to the Sandton Chronicle.

Schwarzenegger, known for starring in films such as Twins, Commando and The Terminator, tweeted to say he was fine.

He said: “Thanks for your concerns, but there is nothing to worry about. I thought I was just jostled by the crowd, which happens a lot.

“I only realized I was kicked when I saw the video like all of you.”

Schwarzenegger added: “I’m just glad the idiot didn’t interrupt my Snapchat.”

The Arnold Classic Africa said the man had been handed over to police.

Schwarzenegger was born in Austria and first rose to prominence as a bodybuilder, winning the Mr Universe title aged 20.

After moving to Hollywood, he achieved worldwide fame in 1982 action film Conan The Barbarian, which launched his film career.

Schwarzenegger served as the 38th governor of California from 2003 to 2011.