(Reuters) - Alphabet's self-driving unit, Waymo, said on Friday it had closed a $5.6 billion funding round led by the Google parent, as it looks to expand its autonomous ride-hailing service.

Automakers and technology companies are investing in autonomous ride-hailing services to capitalize on the technology to drive commercial success, even as it faces widespread skepticism and tight regulatory scrutiny.

The investment round also saw participation from existing investors including Andreessen Horowitz, Fidelity, Perry Creek, Silver Lake, Tiger Global, and T. Rowe Price, Waymo said.

"With this latest investment, we will continue to welcome more riders into our Waymo One ride-hailing service in San Francisco, Phoenix, and Los Angeles, and in Austin and Atlanta through our expanded partnership with Uber," the company said.

Alphabet had planned a $5 billion investment in Waymo over a multi-year period, finance chief Ruth Porat said in July.

Waymo, which offers paid rides in autonomous vehicles in the Bay Area and Los Angeles, as well as in Phoenix, Arizona, spent years logging millions of miles of testing before it received its first permit in 2022 from the California Public Utilities Commission, which regulates ride-hailing services.

Tesla CEO Elon Musk said on Wednesday that the electric vehicle maker will roll out driverless ride-hailing services to the public in California and Texas next year.

General Motors' ( GM ) Cruise is testing cars with human safety drivers after an accident last year led it to pull all vehicles from the road. Meanwhile, Amazon's ( AMZN ) Zoox is expanding testing for its vehicles built without steering wheels and pedals.