Japanese carmaker Toyota is to invest $500m (£387m) in Uber and expand a partnership to jointly develop self-driving cars.

The firm said this would involve the "mass-production" of autonomous vehicles that would be deployed on Uber's ride sharing network.

It is being viewed as a way for both firms to catch up with rivals in the competitive driverless car market.

The deal also values Uber at some $72bn, despite its mounting losses.

That is up 15% since its last investment in May but matches a previous valuation in February.

According to a press release issued by the firms, self-driving technology from each company will be integrated into purpose-built Toyota vehicles.

The fleet will be based on Toyota's Sienna Minivan model with pilot trials beginning in 2021.

Shigeki Tomoyama, executive vice president of Toyota Motor Corporation, said: "This agreement and investment marks an important milestone in our transformation to a mobility company as we help provide a path for safe and secure expansion of mobility services like ride-sharing."

Both Toyota and Uber are seen as lagging behind in developing self-driving cars, as firms such as Waymo, owned by Alphabet, steam ahead.

Uber has also scaled back its self-driving trials after a fatal crash in Tempe, Arizona, in March, when a self-driving Uber SUV killed a pedestrian.

Since then, the ride-hailing giant has removed its autonomous cars from the road and closed its Arizona operations. (BBC)