LONDON — Uber Technologies, the car-sharing service that’s rankling cabbies across the U.S., is fighting its biggest protest yet from European drivers who say the smartphone application threatens their livelihoods.

Traffic snarled in parts of Madrid and Paris Wednesday, with a total of more than 30,000 taxi and limo drivers from London to Berlin blocking tourist centers and shopping districts. They are asking regulators to apply tougher rules on San Francisco-based Uber, whose software allows customers to order a ride from drivers who don’t need licenses that can cost 200,000 euros, or about $270,000, apiece.

While similar demonstrations this year have led to smashed windshields and traffic chaos in Paris, a united front in Europe highlights the challenges for Uber’s expansion after a funding round that values the company at $17 billion, almost five times the figure in an earlier round. Out of some 128 cities it serves, 20 are in Europe, including Manchester, Lyon and Zurich.

“European cities have tended to regulate taxi drivers much more than the U.S.,” said Charles Lichfield, an analyst at Eurasia Group in London. “I do think the protests have a better chance of succeeding.”

About 1,200 Parisian drivers were blocking the Charles de Gaulle and Orly airports this morning and preventing private car services from picking up passengers, said Nadine Annet, vice president at the FNAT taxi association in France. Cabbies also slowed down traffic the A1 highway that circles Paris, leading to a 120-mile jam, local TV reported. The vast majority of France’s 55,000 professional taxis and Paris’s 15,000 cabs are on strike Wednesday, Annet said.

Kader Djielouli, 44, a protester who’s been driving taxis in Paris for 15 years, saying he’s spending most of the day on strike. Djielouli said he’s lost 40 percent of his revenue since 2009 because of services like Uber.

Private car services “are taxis without being taxis,” he said at a cab stand near the Opera metro station in Paris. “We are against them. There needs to be the same rules for all.”

In Madrid, thousands of drivers marched to block the Paseo de la Castellana, one of the city’s main central avenues, as police escorted the demonstration by cars, a helicopter and officers on foot. Protesters chanted insults targeted at Uber and chased taxis that weren’t taking part in the rally.

In Berlin, more than 500 taxis lined up in columns of 20 in the plaza stretching out from the Olympic stadium. Four youth chanting “friends of Uber” were escorted away by security under shouts of a few enraged drivers.

Berlin cabs also targeted airports and the upscale Kurfuerstendamm shopping district. At the Tegel airport, one of the three starting locations for the Berlin demonstration, taxi driver Kubilay Sarikaya said this morning he was skeptical about the protests. While he’d been working since 3 a.m., he said he’ll go along if his friends do.

“While we are demonstrating, the other guys are hauling people around,” said Sarikaya, 33. “There have to be other ways. Ultimately I think folks know that they can always count on the good old cab to get them where they need to be.”

In Milan, no taxi was to be seen after about 5,000 drivers this morning went on a strike that is set to last until 10 p.m.

Yet, it could be London — where drivers started planning the protest weeks ago — that draws the biggest crowd. Between 10,000 and 12,000 black cabs and private hire cars are expected to descend on the tourist hubs of Trafalgar Square and Parliament Square at 2 p.m., said Steve McNamara, general secretary of the Licensed Taxi Drivers Association.

The city’s police, saying protesters haven’t asked for proper permission to assemble, threatened to arrest demonstrators who start assembling before 2 p.m. and don’t leave by 3 p.m. or stray from certain streets. Authorities also plan to cut off entry once the area gets too crowded, the Metropolitan Police said in a statement Wednesday.