Johannesburg - A big earth tremor rocked various places around Johannesburg just a few minutes before 7am on Friday.

The tremor, which lasted for around four or five seconds, happened at 06:56am and was felt across many places in and around the city.

Social media users started tweeting that they had felt it too, with some saying they thought they were the only ones who had felt it or perhaps they felt it because they were "high".

"It was so scary [I] even ran out of the house," @miss_don tweeted.