Paris — An official said a large police operation was underway early Wednesday in the Paris suburb of Saint Denis and it was believed to be linked to the deadly attacks on the French capital.

The police official said there had been exchanges of gunfire and special SWAT teams were on the scene. The official was not authorized to be publicly named, according to police policy. Some media outlets were reporting some had been wounded. Residents were advised to stay inside their homes.

Police had blocked off the area around Place Jean Jaures in Saint Denis, just north of Paris, about 6 a.m. local time.

French authorities have said they are searching for at least two people involved in last Friday's attacks, which killed at least 129 people and 7 terrorists.

Ambulances could be seen and sirens heard in French television footage from the scene.

Separately, two Air France flight bound for Paris from the U.S. had to be diverted Tuesday night because of anonymous threats received after they had taken off, but both planes landed safely in North America, officials said. 

One plane, Air France Flight 65 from Los Angeles International Airport to Charles de Gaulle Airport in Paris, was diverted to Salt Lake City International Airport, Air France said in a statement.

At about the same time a second flight, Air France 55, took off from Dulles International Airport outside Washington and was diverted to Halifax on Canada's East Coast, officials said.

Passengers got off both planes safely and were taken to terminals. Authorities in both the U.S. and Canada were preparing to search the planes with dogs, officials said.

The FBI was taking over the investigation of the plane in Salt Lake City, which was diverted because of a threat received by phone after takeoff, Salt Lake airport spokeswoman Bianca Shreeve said.

Keith Rosso of Santa Monica, Calif., a passenger on the flight from Los Angeles with his fiancee, said "everything was smooth, everything was great, everything was going swell" for the first two hours of the flight, then things changed.

"The flight attendants quickly came by and cleared plates, then there was an announcement that we were making an emergency landing and that the flight attendants were trained exactly for situations like this," Rosso told The Associated Press by phone from the airport in Salt Lake City.

He said he looked at the flight monitor at his set and "we had made a pretty sharp right turn — we had been almost near Canada — toward Salt Lake City."

Rosso said an FBI agent interviewed the passengers after the landing.

In Halifax, the Royal Canadian Mounted Police were leading the investigation.

RCMP Constable Mark Skinner said there were 262 people onboard that plane, which also received an anonymous threat. No further details on the threat were released.

"We received a complaint of a bomb threat and we responded to it," Skinner said. "They have to go to through the plane. I don't think there is any timeline on when that plane might get back in the air."

The threats came after last week's attacks in Paris that killed 129 people and heightened security concerns around the world.

Associated Press Writers Stepanie Siek in New York, Robert Gillies in Toronto and Andrew Dalton in Phoenix contributed to this report from New York.