More than 120 people have been killed in a series of coordinated terrorist attacks across Paris, including a massacre at a rock concert.

Key points: Multiple attacks across Paris kill at least 120 people, officials say

Eight militants killed, including four at Bataclan

More than 200 people injured, including one Australian

The Bataclan concert hall in eastern Paris was playing host to sold out crowds who had turned out to see US rock band Eagles of Death Metal on Friday night (local time).

Gunmen and bombers also attacked busy restaurants and bars, and explosions were heard near a stadium in what a shaken French president Francois Hollande described as an unprecedented terrorist attack.

More than 350 people were injured in the attacks, about 100 of those seriously.

One Australian, Emma Grace Parkinson, 19, from Hobart, was believed to have been shot and was taken to hospital for treatment.

A witness inside the concert hall said black-clothed gunmen stormed the building and calmly fired AK-47s into the crowd.

Another witness said they heard one of the attackers shout in Arabic "Allahu akbar" (God is greatest), while another person said they heard a gunman blame France's intervention in the Syrian civil war as the reason for the attack.

Several explosions were heard after a police assault of the venue got underway, with reports later emerging that four gunmen, each wearing explosive belts, died.

Three of the attackers blew themselves up while a fourth was hit by police fire and "blew up as he fell", a source told AFP.

Eight militants in total were killed around Paris, including seven by their suicide belts, an AFP source said.

Earlier, 18 people were killed when a gunman opened fire on Friday night diners sitting at outdoor terraces in the popular Charonne area, not far from the Bataclan concert hall.

And in the north of the city, several people were killed in three explosions near the Stade de France where France were playing Germany in an international football match, security sources said.

President Hollande was attending the match and had to be hastily evacuated.

A witness said one of the detonations blew people into the air outside a McDonald's restaurant opposite the stadium.

The match continued until the end, but panic broke out in the crowd as rumours of the attack spread, and spectators were held in the stadium and assembled spontaneously on the pitch.

Gunmen 'very calm' while reloading at concert 'bloodbath'

A French radio reporter who was inside the Bataclan concert hall gave a harrowing account of the "10 horrific minutes" when gunmen entered and fired calmly and randomly at hundreds of screaming concertgoers.

"It was a bloodbath," Julien Pearce, a reporter for France's Europe 1 radio station, told CNN.

"People yelled, screamed and everybody [was] lying on the floor, and it lasted for 10 minutes, 10 minutes, 10 horrific minutes where everybody was on the floor covering their heads.

"We heard so many gunshots and the terrorists were very calm, very determined and they reloaded three or four times their weapons and they didn't shout anything. They didn't say anything."

Pierce recounted seeing 20 to 25 bodies on the floor and others very badly injured.

Toon, a 22 year-old messenger who lives near the Bataclan, was going into the concert hall with two friends at 10:30pm when he saw three young men dressed in black and armed with machine guns. He stayed outside.

One of the gunmen began firing into the crowd.

"People were falling like dominoes," he said.

Mr Hollande has declared a state of emergency for all of France and has reimposed border controls, which will restrict freedom of movement as people attempt to enter from other EU countries.

Several Metro lines in Paris have been closed and an additional 1,500 soldiers mobilised around the city.

Survivors from the concert hall massacre were bussed away from the scene, with those uninjured taken to police stations to be interviewed.

'Our fight will be merciless', president says

Mr Hollande, who was evacuated from the Stade de France after several explosions were heard nearby, later visited the concert hall after the police operation.

He said the official response would be "merciless".

"We wanted to be here among all those who saw these atrocious things to say that we are going to fight and our fight will be merciless because these terrorists that are capable of such atrocities need to know that they will be confronted by a France that is determined, unified and pulls together," he said.

Speaking earlier on TV, the French president called the attacks "unprecedented" in scale.

"It's horrific," he said.

"We have, on my orders, mobilised all the forces we can muster in order to neutralise the terrorist threat and secure all the affected areas.

"I have also asked for military reinforcements.

Timeline: Paris attacks 9:20 pm Paris time: A suicide bomber activates an explosive belt near Stade de France, killing the bomber and a passer-by. French president Francois Hollande was at the match and moved to safety

9:25 pm: A gunmen opens fire at the Le Carillon bar and Petit Cambodge restaurant, killing 15 and severely injuring 10

9:30 pm: Outside the Stade de France, a second suicide bomber detonates a bomb, killing himself

9:32 pm: Gunmen open fire in front of the A La Bonne Biere bar, killing five people and severely injuring eight

9:36 pm: Gunmen kill 19 people sitting on the terrace of the La Belle Equipe restaurant. Nine people are also severely injured

9:40 pm: Several gunmen enter the Bataclan concert hall, killing about 89 people and wounding many. About the same time, a suicide bomber kills himself at the Le Comptoir Voltaire restaurant, injuring one person severely.

9:53 pm: A third suicide bomber kills himself near the Stade de France

11:57pm: Mr Hollande declares a state of emergency

1:20 am: Security forces launch an assault at the Bataclan concert hall to try and free those inside. Three of the attackers are killed 10:00pm Paris time is 8:00am AEDT



"They too are in the Paris area to make sure no new attack can take place."

In declaring the state of emergency and closing the borders, Mr Hollande said travel may also be banned.

"We have to assure ourselves that no-one can enter, nor to commit any act whatever that may be at the same time that these crimes that alas have taken place, can be stopped."

Australia's Foreign Minister, Julie Bishop, said one Australian was injured in the attacks.

"I am aware of an Australian who has been injured in the Paris attacks and we are providing consular assistance," Ms Bishop said in a statement.

"The Australian Government is continuing to work with French authorities to identify any other Australians who may be affected."

'We pulled a table over our heads to protect us'



Ben Grant and his wife were in one of the bars when a gunman opened fire.

"I heard the gunshots, people jumped to the ground and we managed to put a table over our heads to protect us ... and we held up because of a pile of bodies in front and pretty much for my wife to walk over and we waited to just now when we got led out," Mr Grant said.

Analysis from Europe correspondent Barbara Miller:

President Francois Hollande has described these attacks as unprecedented.



Paris did face those terrible attacks at the beginning of the year on the offices of Charlie Hebdo and then at a kosher supermarket.



This is on a much bigger scale. Francois Hollande declared a state of emergency and said borders were being closed.



There was a certain amount of alarm that that meant perhaps people weren't going to be allowed to get in and out of France.



What that seems to mean is that border controls are being imposed. I think the main concern here is not people going into France but ... whether anyone is trying to leave France who might be connected to those attacks.



It comes on the day that the US and Britain suggested that they had killed the man known as Jihadi John, who is the man who appears in several beheading videos of Western tourists.



There will be speculation and research going into whether there is a link there.



It also comes ahead of Paris hosting a major climate conference.



It is still far too early to say whether these attacks were launched because of any of those reasons or simply because the people who planned them and executed them found themselves ready to do so.

A resident who lives near the Petit Cambodge restaurant, close to the popular Place de La Republique, told ABC News 24 he could see about 10 bodies from his window.

"I was in my room, in the streets where the shots happened. I was about to go, to leave my place and join friends and I just went to the window to see what's happening and I saw the shots," he said.

"I can't even go in the street because my street is closed."

Counter-terrorism prosecutors said they had opened a preliminary investigation.

The mayor of Paris, Anne Hidalgo, called for residents to stay at home.

France has been on high alert since the jihadist attacks in January against Charlie Hebdo magazine and a Jewish supermarket that left 17 dead.

Several other attacks have been foiled through the year.

US president Barack Obama said he would provide "whatever assistance the Government and the people of France need".

"France is our oldest ally. The French people have stood shoulder to shoulder with the US time and again," he said.

"Now we want to be very clear that we stand together with them in the fight against terrorism and extremism."

More than 500 French fighters are thought to be with IS in Syria and Iraq, according to official figures, while 250 have returned and some 750 expressed a desire to go there.

The government announced last week that it was restoring border checks as a security measure for UN climate talks that start in Paris at the end of this month.

The Australian Government's Smartraveller website advises Australians to exercise "normal safety precautions" if travelling to France.

But it said "Australians in Paris should minimise movement in public places" and that "further violent incidents could occur".

Australians with concerns for family or friends in Paris can call the Department of Foreign Affairs helpline on 1300 555 135.

ABC/wires