PARIS, Nov 18 - Heavy gunfire erupted in a north Paris suburb early on Wednesday as special police forces launched an operation to catch the alleged mastermind behind gun and bomb attacks in which 129 people were killed last week, police and judicial sources said.

Several suspected attackers and potential accomplices remained holed up in an apartment after the shoot-out, a police source said.

Belgian militant Abdelhamid Abaaoud, 27, initially thought to have pulled the strings in Friday night's attacks in the French capital from Syria, was believed to be one of those barricaded in an apartment in St Denis, said a judicial source.

The Paris attacks, claimed by Islamic State militants, raised security concerns around the world, with an international soccer match called off in Germany on Tuesday and two Air France flights from the United States diverted for several hours due to bomb threats.

In Syria, France and Russia bombed targets to punish Islamic State for the coordinated Paris massacre and the downing of a Russian airliner over Sinai on Oct. 31.

French TV stations BFMTV and iTele both showed amateur video of Wednesday's early morning shooting and cited witnesses in the area as saying they had heard sporadic gunfire from around 4:30 a.m. (0330 GMT).

"The operation is still under way. It's not over," local member of parliament Mathieu Hanotin said on France Inter radio. "Everyone must stay indoors. There are still gunmen holed up in the apartment."

BFMTV said some police had been wounded during the operation, which took place near the Stade de France sports stadium where three suicide bombers detonated their explosive belts and killed a passer-by on Friday.

French prosecutors have identified five of the seven dead assailants from Friday - four Frenchmen and a man who was fingerprinted in Greece among refugees last month.

But they now believe two men directly involved in the assault subsequently escaped.

Wednesday's operation came after a source with knowledge of the investigation said a cell phone had been found with a map of the music venue targeted in one of the attacks and a text message on it saying words to the effect of "let's go".

The source said the phone was found in a dustbin near the Bataclan concert hall where the bloodiest of the shootings took place.

Islamic State said it carried out the attacks in retaliation for French and Russian air raids in Iraq and Syria. Investigators said the Paris plot was hatched in Syria and nurtured in Belgium.

Security alerts

Late on Tuesday, the U.S. Federal Aviation Administration (FAA) said two Paris-bound Air France flights were diverted following anonymous bomb threats, and hundreds of passengers and crew were safely removed.

Flight 65, an Airbus A-380 that had departed from Los Angeles, landed safely in Salt Lake City where passengers and crew were escorted into the terminal, an FAA spokesman said.

The FBI said in a statement that no evidence was found aboard the plane "which would lend credibility to the threats" against the flight.

A separate flight that left Dulles International Airport outside Washington, D.C., Flight 55, was diverted to Halifax International Airport in Nova Scotia, Canada, where passengers and crew had also disembarked. The Halifax Airport tweeted that 262 passengers and crew members had been aboard.

The Royal Canadian Mounted Police in Halifax said on its Twitter feed that police dogs searched the plane for evidence of explosives, but no details were disclosed.

In a brief statement, Air France said both flights had been the "subjects of anonymous threats received after their respective take-offs".

Flights to Paris from Asia operated as normal on Wednesday.

Earlier, bomb fears had prompted German police to call off a soccer match between Germany and the Netherlands in Hanover two hours before kick-off. German Chancellor Angela Merkel had been due to attend.

No arrests were made and no explosives were found.

"We had received specific indications that an attack with explosives was planned," Hanover Police President Volker Kluwe told NDR state broadcaster. "We took them seriously, and that is why we took the measures."

France and Germany were playing a soccer friendly at the Stade de France when Friday's attacks took place.

Air strikes in Syria

Syrian targets hit by Russian long-range bombers and cruise missiles on Tuesday included the Islamic State stronghold of Raqqa. French warplanes also targeted Raqqa on Tuesday evening in the third such bombing raid within 48 hours.

Paris and Moscow are not coordinating their operations, but French President Francois Hollande has called for a global campaign against the radicals in the wake of the Paris attacks.

Russian President Vladimir Putin vowed to hunt down those responsible and intensify air strikes against Islamists in Syria.

Hollande will visit Putin in Moscow on Nov. 26, two days after the French leader is due to meet U.S. President Barack Obama in Washington to push for a concerted drive against Islamic State, which controls large parts of Syria and Iraq.

Obama said in Manila on Wednesday he wanted Moscow to shift its focus from propping up Syria's government to fighting Islamic State and would discuss that with Putin.