Saudi Arabia's largest telecommunications firm STC plans to buy a 10 per cent stake in car booking firm Careem, the company said on Sunday.

Careem is a competitor of US-based Uber, a smartphone app that connects passengers and drivers.

In a notice to the Saudi stock exchange, Saudi Telecom Co said the proposed stake is worth $100 million, to be funded by STC's "internal financial resources".

The investment is the latest high-profile Saudi venture since Riyadh in April announced its Vision 2030 plan to diversify the oil-dependent economy and broaden its investment base.

"This move is in line with the company strategy to invest in the innovative digital world," STC said, adding it would "enhance communication via mobile within the transport system."

Uber announced in June that Saudi Arabia's Public Investment Fund would inject $3.5 billion to help the app's global expansion.

Its rival Careem was founded in 2012 and has operations in 47 cities across the Middle East, North Africa, Turkey and Pakistan, STC said.

STC is the largest Arab telecommunications firm in terms of capitalisation.

It has more than 100 million customers in nine countries including Turkey, South Africa, India and Malaysia.

Car booking apps are popular in Saudi Arabia, particularly among women who are banned from driving in the kingdom.