NEW YORK -- Some drivers for ride-hailing giants Uber and Lyft turned off their apps Wednesday to protest what they say are declining wages at a time when both companies are raking in billions of dollars from investors.

Demonstrations took place in 10 U.S. cities, including Chicago, Los Angeles, New York, San Francisco and Washington, as well as some European locations like London. But they did not seem to cause much disruption and many riders were still able to hail a car with ease.

The protests arrive just ahead of Uber's initial public stock offering Friday. Uber hopes to raise $9 billion, putting the company's valuation in excess of $91 billion.

It's not the first time drivers for ride-hailing apps have staged protests. Strikes were planned in several cities ahead of Lyft's IPO last month, although the disruption to riders appeared to be minimal then, too. More cities are participating in Wednesday's protest.

"Drivers built these billion dollar companies and it is just plain wrong that so many continue to be paid poverty wages while Silicon Valley investors get rich off their labour," said Brendan Sexton, executive director of the Independent Drivers Guild. "All drivers deserve fair pay."

The Guild organized a caravan of Uber drivers across the Brooklyn Bridge Wednesday.

Some drivers went offline in New York between 7 a.m. and 9 a.m., though it was still easy to locate a driver during rush hour near Wall Street in lower Manhattan.

Drivers in Los Angeles are participating in a 24-hour strike and picket line at Los Angeles International Airport.

In the UK, the Independent Workers Union said some Uber drivers are observing a nine-hour boycott. The union demands, among other things, increased fares per mile and a decrease in commissions paid to Uber.

Uber, in a prepared statement, said it is constantly working to improve the working environment for drivers.

"Drivers are at the heart of our service -- we can't succeed without them -- and thousands of people come into work at Uber every day focused on how to make their experience better, on and off the road."

Lyft said its drivers' hourly earnings have increased over the last two years, that 75% of its drivers work less than 10 hours per week to supplement existing jobs and that on average the company's drivers earn over $20 an hour before subtracting expenses such as gas and vehicle maintenance.

"We know that access to flexible, extra income makes a big difference for millions of people, and we're constantly working to improve how we can best serve our driver community," Lyft said.

Labour actions also took place in Atlanta, Boston, Philadelphia, San Diego and Stamford, Connecticut.