About 100 people were killed in the Bataclan concert hall in central Paris and 40 others have died in other locations in and around Paris in a militant attack, an official at Paris City hall said on Saturday.

Gunmen and bombers attacked busy restaurants, bars and a concert hall at locations around Paris on Friday, killing dozens of people in what a shaken President Francois Hollande described as an unprecedented terrorist attack.

The apparently coordinated gun and bomb assault came as the country, a founder member of the US-led coalition waging air strikes against Islamic State fighters in Syria and Iraq, was on high alert for terrorist attacks ahead of a global climate conference due to open later this month.

Hollande, who was attending an international soccer match with German Foreign Minister Frank-Walter Steinmeier when several explosions took place outside the national stadium, declared a state of emergency in the Paris region and announced the closure of France's borders to stop perpetrators escaping.

"This is a horror," the visibly shaken president said in a midnight television address to the nation before chairing an emergency cabinet meeting.

All emergency services were mobilised, police leave was cancelled and hospitals recalled staff to cope with the casualties.

Hollande said police were launching an assault at one of the attack sites as he spoke. A Reuters witness heard five explosions outside the Bataclan music hall, where up to 60 people were being held hostage.

A second Reuters reporter later said police had completed an operation at the building. BMF TV said two gunmen had been killed.

Earlier, witnesses said an elite anti-terror unit had taken up positions outside the popular concert venue, which was attacked by two or three gunmen, who were reported to have shouted slogans condemning France's role in Syria.

"We know where these attacks come from," Hollande said, without naming any individual group. "There are indeed good reasons to be afraid."

HIGH ALERT

France has been on high alert ever since Islamist gunmen attacked the satirical weekly Charlie Hebdo and a Kosher supermarket in Paris in January, killing 18 people.

US President Barack Obama and German Chancellor Angela Merkel led a global chorus of solidarity with France and U.N. Secretary-General Ban Ki-moon condemned the "despicable attacks" and demanded the release of the hostages.

Julien Pierce, a journalist from Europe 1 radio, was inside the concert hall when the shooting began. In an eyewitness report posted on the station's website, Pierce said several very young individuals, who were not wearing masks, entered the hall while the concert was under way armed with Kalashnikov assault rifles and started "blindly shooting at the crowd".

"There were bodies everywhere," he said.

French media reported five more or less simultaneous attacks in mid-evening in central Paris and outside the Stade de France stadium in the suburb of Saint-Denis, north of the city centre.

There was no immediate verifiable claim of responsibility but supporters of the Islamic State militant group which controls swathes of Iraq and Syria said in Twitter messages that the group carried them out.

"The State of the caliphate hit the house of the cross," one tweet said.

Three explosions were heard near the Stade de France, where the France-Germany friendly soccer match was being played. A witness said one of the detonations blew people into the air outside a McDonald's restaurant outside 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.

TF1 television said up to 35 people were dead near the soccer stadium, including two suspected suicide bombers.

Police helicopters circled the stadium as Hollande was rushed back to the interior ministry to deal with the situation.

In central Paris, shooting erupted in mid-evening outside a Cambodian restaurant in the capital's 10th district. There were unconfirmed reports of other shootings in Rue de Charonne in the 11th district and at the central Les Halles shopping and cinema complex.

"There are lots of people here. I don't know what's happening, a sobbing witness who gave her name only as Anna told BFM TV outside the Bataclan hall. "It's horrible. There's a body over there. It's horrible."

The attacks came within days of attacks claimed by Islamic State militants on a Shi'ite Muslim district of southern Beirut in Lebanon, and a Russian tourist aircraft which crashed in Egypt's Sinai Peninsula.

Earlier on Friday, the United States and Britain said they had launched an attack in the Syrian town of Raqqa on a British Islamic State militant known as "Jihadi John" but it was not certain whether he had been killed. – Reuters