Tesla has unveiled its first articulated electric lorry with production due to begin in the US in 2019.

The company's billionaire chief executive Elon Musk said the Semi truck is capable of travelling 500 miles on an electric charge.

He also said it will cost less than a diesel truck considering fuel savings, lower maintenance and other factors.

"We're confident that this is a product that's better in every way from a feature standpoint," he told a crowd of Tesla fans in California.

Mr Musk did not reveal the vehicle's price but said customers can put down a 5,000 dollar (£3,778) deposit.

Key features

The truck will have Tesla's Autopilot system, which can maintain a set speed and slow down automatically in traffic.

It also has a system that automatically keeps the vehicle in its lane.

Mr Musk said several Tesla lorries will be able to travel in a convoy, autonomously following each other.

The company also plans to create a global network of solar-powered "megachargers" that could get the trucks back up to 400 miles of range after charging for only 30 minutes.

Tesla also surprised fans with an updated version of its first sports car, the Roadster.

The company has spent more than a decade making cars - and more recently, solar panels.

It now looking to diversify into big trucks to help its goal of shifting to sustainable transport.

Mr Musk is involved in many other projects and announced plans he says could allow his SpaceX company to colonise Mars in September.

The tech entrepreneur's projects also include high-speed transit, artificial intelligence research and a new company that is digging tunnels beneath Los Angeles to alleviate traffic congestion.