French security forces, who are hunting for a ninth terrorists involved in last Friday’s Paris attacks, launched a massive operation in the Parisian suburb of St-Denis on Wednesday. Residents reported hearing exchanges of gunfire and said special SWAT teams were on the scene, according to Associated Press. Residents were asked to stay inside their homes, while firing from automatic guns could be heard. Agence France-Press reported that some policemen were injured in the exchange. French authorities said at least nine terrorists were involved in the attacks, of which six died in suicide bombings and one was killed by police. One suspect, identified as Salah Abdeslam was last seen heading back to Brussels and remains on the run, The Guardian reported.

However, the numbers and details of attackers vary and officials have not released only limited information about the terrorists. Two men have been arrested in Belgium for the attacks, while several arrests were made in Germany on Tuesday. France and Russia on Tuesday launched new airstrikes on suspected Islamic State targets in Syria, reported Associated Press.

France and parts of the European Union remain on high alert, with the Eiffel Tower being closed to the public, the Louvre being heavily patrolled, and a soccer match between Germany and Netherlands in Hanover being cancelled. Two Air France flights headed to Paris from the United States were also diverted early on Wednesday after receiving anonymous threats .