World's richest person Elon Musk, who recently bought Twitter in a multi-billion-dollar deal, kicked off a storm on social media on Monday by posting a speculative tweet over the possibility of his death under mysterious circumstances .

Musk, 50, who is the CEO of US-based electric car major Tesla and American aerospace company SpaceX, said in a tweet: If I die under mysterious circumstances, it's been nice knowin ya .

When his mother Maye Musk responded to the post, saying "it's not funny!", he apologised.

Sorry! I will do my best to stay alive," Musk replied to his mother.

The South Africa-born American billionaire, however, did not specify further about his tweet, leaving social media users with many questions about the nature and timing of his post on the popular microblogging site which he bought last month for USD 44 billion.

According to the prestigious Forbes magazine, Musk is the world's richest person with an estimated net worth of USD 273.6 billion.