French Prime Minister Manuel Valls said on Thursday that the country is facing the risk of being attacked with 'chemical or biological weapons'.

During a debate over the extension of a state of emergency, Valls told French lawmakers that the risk of chemical or biological attack cannot be ruled out.

As the country steps up the investigation into the attacks in Paris which were claimed by the Islamic State group, the French PM also urged the European Union to adopt measures facilitating the sharing of information related to air passengers.

"More than ever, it's time for Europe to adopt the text... to guarantee the traceability of movements, including within the union. It's a condition of our collective security,' he said.

Meanwhile, according to a directive from police commanders issued on Thursday, French police will now be allowed to carry weapons even when they are off duty.

They will be allowed to use their guns in the event of a terror attack providing they wear a police armband to avoid 'any confusion', the note says.

Terror attacks rocked the French capital on Friday killing over 150 people, which President Francois Hollande termed as 'an act of war'.

Image: Forensics of the French police are at work outside a building in Saint-Denis, near Paris, on Thursday. Photograph: Benoit Tessier / Reuters