Anti-terrorist police are hunting down the 9th suspect of the Paris attacks in the city's northern suburbs Saint-Denis, BFMTV reported early Wednesday morning.

The operation targets Abdelhamid Abaaoud, a Moroccan-origin Belgian jihadist believed to be the mastermind behind Friday night's attacks, according to the report.

So far three suspects have been arrested and some police officers have been injured in the operation, it said.

Witnesses told BFMTV they have been hearing "explosions" and "gunshots" since 4:30 am local time (0330 GMT). Gunshots could also be clearly heard from the Xinhua office in Paris.

Gunshots and explosions were heard again around 7:28 am local time (0628 GMT), according to a Xinhua journalist on the site.

The operation was taking place in the "very center" of the city, Saint-Denis Mayor Didier Paillard told BFMTV, noting that residents are advised to stay at home.

Public transport was suspended in the operation zone. Police also suggested people working in the area not go to work.

Another key suspect, Salah Abdeslam, who might be one of the shooters last Friday night that killed innocent people in terraces of cafes and restaurants, is still at large.

Simultaneous shootings, one of which turned into a hostage taking, and explosions at restaurants, Bataclan concert hall and the national stadium in Paris on Friday night killed at least 129 people and injured hundreds of others.