Crowds braved queues at security checks and heavy rain showers as they lined the banks of the Seine river in Paris on Friday to watch an extravagant Olympics opening ceremony that began with an explosion of smoke in the colours of the tricolor flag.

Olympics fever has been slow to build in Paris where local residents have complained about street closures in the heart of the city and local businesses have bemoaned a lack of trade as the French capital was transformed into an open-air fortress.

A flotilla of barges are carrying more than 6,000 athletes along the Seine river in a nearly four-hour show, with Lady Gaga singing and dancers set to perform from the city's rooftops.

"I just can’t wait to see how amazing the show will be," said Fejiro Ogbanufe, 37, a Nigeria flag draped over her shoulders, who travelled from Geneva with her three daughters.

Elise Boukorrass, 17, said she was "super excited, it happens once in a lifetime" after passing through police checks.

"The security checks were a bit long but it's worth it."

France has rolled out an unprecedented peacetime security operation to secure the event. Some 45,000 police and thousands of soldiers have been deployed, airspace around the Greater Paris region shut down, and snipers positioned on rooftops.

"There are more cops than people, I don't feel in danger," said Jean Landerretche, a 19-year-old biochemistry student from Paris.

"I can't wait to see how they managed to take the ceremony out of the stadium, I think it's going to be a huge party," said Julie Tourtet, 27, who is volunteering at the Games. "It's really the Olympic spirit: it brings people together, it's moving, we're going to get a huge rush of emotion."

But not everybody shared the excitement.

Yi, a Chinese national living in Paris, left the riverbank because there were too many people for a clear view.

“There are so many people, we can’t see anything on the river," she said. "We live very close in the area so we got four free tickets but we are heading home, we’d rather watch it on our TV than on a screen here.”

"We are here today and it's just so so," 26-year-old Aimee Wang, from China, said of the atmosphere in Paris.

She and a friend planned to watch a few of the sporting events but were not so excited about the opening ceremony.

"It's so expensive today. We're probably just going to watch in our friend's house," said her friend Henry Pan, also 26.

Others didn't need tickets to watch the show live.

Alexandre Pichot, 48, did not realise when he moved into a houseboat on the Seine that he would have front row seats to the opening ceremony. "It's really great. We have some good food, good French wine, good friends," he said. "It's perfect."