Paris terrorist shooting
French President Francois Hollande has blamed Islamic State for the Paris massacreReuters

The devastating attacks that took place in Paris last night are expected to have taken weeks to plan, but the French authorities were aware of the individuals behind the marauding massacre that left 120 people dead – the majority killed at in the Bataclan concert hall. Islamic State (Isis) claimed responsibility for the attack after French President François Hollande said the terrorist group had committed an "act of war" against France.

Speaking minutes after news of the horrific incidents had broken last night, Hollande told the French nation: "We know where it comes from, who these criminals are, who these terrorists are. As I speak, terrorist attacks of unprecedented proportions are underway in the Paris area. There are dozens killed, there are many injured. It is a horror. We have, on my decision, mobilised all forces possible to neutralise the terrorists and make all concerned areas safe."

Paris was targeted by Isis terrorists in January, who stormed the offices of satirical magazine Charlie Hebdo, killing 12 and injuring 11 including a French policeman who was executed in the street.

Speculation has already begun on how much the French authorities knew about the eight terrorists who died in last night's attacks, and if they had been on a "watch list" due to the heightened security following the January massacre. Brothers Cherif Kouachi and Said Kouachi, who carried out the Charlie Hebdo attack, were known to US intelligence services and had been under surveillance since as early as 2010.

France is now on lockdown, following the worst atrocity in the French capital since the World War Two, after Parisians were shot dead in five sites in Paris.

At least 80 fans attending the concert by heavy rock band the Eagles of Death Metal at the Bataclan concert hall were slaughtered by the terrorists at the venue. Four of the terrorists died: three blew themselves up using 'suicide belts' and a fourth was shot dead by French police.

In separate attacks, terrorists targeted the restaurant La Belle Equipe on the Rue de Charonne in the 11th district of Paris, leaving at least 19 people dead; Le Carillon bar and Le Petit Cambodge restaurant in the 10th district's Rue Alibert, killing 12; and La Casa Nostra restaurant on the Rue de la Fontaine au Roi in the 11th district, where at least five people were gunned down.

The terrorists, who were armed with grenades and Kalashnikov AK-47 automatic rifles – the same weapon used in the Charlie Hebdo terror attacks.

Gunmen also targeted football stadium Stade de France during an international friendly between the French national side and Germany that was attended by French President François Hollande. Hollande was rushed to safety by bodyguards. Six fans where killed when a suicide bomber detonated explosives outside the stadium.

The French government has declared three days of national mourning.