Suspects of Charlie Hebdo attack still at large despite intensive search

The two main suspects of the armed attack at the headquarters of the Paris-based Charlie Hebdo satirical weekly were still at large so far, after an intensive search operation finished in the Picardie region northeast of Paris.

France has deployed tens of thousands of troops in the hunt for the two brothers, Cherif Kouachi, 32, and his 34-year-old brother Said, accused of killing 10 journalists and two policemen on Wednesday morning at the offices of Charlie Hebdo.

The manhunt came as the head of Britain's domestic spy agency MI5 warned that Islamist militants were planning other "mass casualty attacks against the West", and that intelligence services may be powerless to stop them.

In the rural Aisne region of Picardie, elite armed police and paramilitary forces backed by helicopters searched a wooded area near which the fugitives had earlier robbed a petrol station and abandoned their getaway car following Wednesday's shooting in the capital.

According to the French television BFMTV, one of its journalists witnessed the departure of police vehicles from the area searched on Thursday night. However, police presence is maintained there to deal with any eventuality.

The brothers were thought to have carried out the deadliest attack since 1995, in revenge for the weekly's repeated publication of cartoons mocking the Prophet Mohammed.

Charlie Hebdo, which is based in Paris' 11th arrondissement, was firebombed in 2011, due to the publishing of a controversial series of cartoons depicting Prophet Mohammed.

In its last published cartoons, the weekly mocked Abu Bakr al- Baghdadi, leader of the Islamic State, which seized major towns in Iraq and Syria.

One of the three suspects, 18-year-old Hamyd Mourad, turned himself in to police late on Wednesday.

According to reports, Cherif Kouachi had previously been tried on terrorism charges and served 18 months in prison.

France increased on Thursday its security alert system, Vigipirat, to attack alert in its northern region of Picardie.