Tech billionaires including Elon Musk, Mark Zuckerberg and Jeff Bezos were given prime positions at Donald Trump's inauguration Monday, in an unprecedented demonstration of their power and influence on US politics.

Musk, Bezos and Zuckerberg are the world's three richest people, according to Forbes. Google co-founder Sergey Brin, who also attended, ranks seventh.

US tech tycoons have spent the weeks since the election courting favor with Trump, marking a dramatic shift from Silicon Valley's more hostile response to his first term as president four years ago.

Attendees also included Apple CEO Tim Cook and Google CEO Sundar Pichai.