Seven people have been arrested over the Charlie Hebdo massacre

Seven people have been arrested over the Charlie Hebdo massacre as two 'armed and dangerous' brothers with links to terrorist groups going back at least a decade today remained on the run.

As the manhunt for Cherif and Said Kouachi continued, their alleged getaway driver Hamyd Mourad, 18, turned himself into police in Charleville-Mezieres in northern France.

All three French-Algerian Muslims escaped yesterday following the bloodbath at the offices of the notoriously anti-Islamist satirical magazine in Paris.

In 2008, Cherif was sentenced to three years in prison for terror offences – but served just 18 months.

Questions will be asked why – once again – young Frenchmen with close links to radical Islam and its terrorist affiliates were apparently given free rein to carry out their crimes.

The fact that two were still at large almost 24 hours after a gun battle in which two policemen died alongside ten others, mainly magazine staff, was also a cause for huge concern. 

In another development, two police officers have been shot by a man brandishing a machine gun on the outskirts of Paris, with one understood to be seriously injured.

The suspect, thought to be wearing a bullet-proof vest and body armour, attacked the municipal police officers in Montrouge just after 8am (7am GMT) as they attended a routine road incident. A man has been arrested. It is not known if the shooting is linked to the Charlie Hebdo attack.

There were also reports this morning of an explosion at a kebab shop near a mosque in Lyon. 

Meanwhile, seven 'friends and associates' of the two main suspects in yesterday's atrocity were detained in Reims, Charleville-Mezieres and the Paris area, police said.

Prime Minister Manuel Valls said France faced a terrorist threat 'without precedent' and confirmed the two Kouachi brothers were known to security services. 

But he added it was too early to say whether authorities had underestimated the threat they posed.

'Because they were known, they had been followed,' he told RTL radio, adding: 'We must think of the victims. Today it's a day of mourning.' 

Detectives identified the Kouachis after one left his identification papers in the abandoned Citroen car used to escape after the attack on Charlie Hebdo.

A French police source said they were 'armed and dangerous' and that a 'nationwide hunt was underway to find them.'

He added that Mourad, a student, was encouraged to hand himself in by relatives after his name appeared on social media as a suspect for the killings. 

He is believed to be the Kouachis' brother-in-law, according to Sky News. Today he was under armed guard and being questioned by police. 

Operations by RAID, the police tactical unit, closed on an address in Reims, eastern France, overnight but it came to nothing, he added. 

The Kouachi brothers also had links with the Paris suburb of Pantin, where another raid took place on a suspected flat which they used as hide out on Avenue Jean-Lolive. 

France is holding a day of mourning for the 12 people killed by automatic gunfire during the country's worst terrorist atrocity this century.

A minute's silence will be observed at midday across the country and the bells of Notre Dame Cathedral in the capital will toll.

Both Said Kouachi, 34, and his brother, Cherif Kouachi, 33, were first arrested in 2005 as suspected members of the Buttes Chaumont – a group operating out of the 19th arrondissement of Paris and sending terrorist fighters to Iraq.  

Cherif was convicted in 2008 to three years in prison, with 18 months suspended, for his association with the underground organisation.

He had wanted to fly to Iraq via Syria, and was found with a manual for a Kalashnikov – the automatic weapon used in Wednesday's attack.