Speaking in dazed, frightened and staccato voices, survivors of the coordinated Paris attacks have begun recalling the sickening horror of a truly nightmarish Friday the 13^th.

The terrorists struck almost simultaneously in six sites in Paris—Stade de France, La Petit Cambodge restaurant and Carillon bar, Rue de la Fontaine au Roi, Bataclan concert hall, Boulevard Voltaire, and La Belle Equipe bar.

The assaults began around 9:15 p.m. on Friday local time with three suicide bombings near the Stade de France, where French President Francois Hollande and a crowd of 80,000 were watching a France-Germany friendly soccer game.

Almost simultaneously, gunmen with automatic rifles jumped from cars near popular bars and restaurants in the capital, shooting at Parisian diners.

Those caught up in the attacks described scenes of "carnage" that some likened to a "civil war."

Witnesses at the Bataclan concert hall—where at least 80 people were killed—described the terror that unfolded before their eyes at the French capital's famous music venue.

One young man who managed to flee said: "I was lying in a grave, the girl next to me was dead. They were shooting repeatedly," the Daily Express reported.

Another witness, with blood all over his jeans, said at the scene: "I had a piece of flesh on me, there was blood everywhere, bodies everywhere."

Theresa Cede, a 39-year-old who works in the telecommunications sector, was also at Bataclan with a friend when the terrorists burst in, shooting people standing near her on a balcony, according to a Bloomberg report.

"I hid underneath the body of a man who was shot in the head. I was covered in blood," Cede said.

Another woman lying next to her was severely wounded.

She said she miraculously escaped unharmed after police stormed the building. "I don't know how many guardian angels I had looking out for me," she said.

All hell broke loose when four men, armed with Kalashnikov assault rifles, entered the concert hall at around 9:30 p.m., 40 minutes into the band set, after killing the bouncers, witnesses said.

Some of the hooded gunmen, with their faces covered by scarves, shouted in French: "All of this it your President's fault," while others spoke of France's military intervention in Syria, according to witnesses.

Benoit, one of the massacre survivors, who managed to escape with a friend, said: "I thought a loudspeaker had exploded, then the lights came up. The gunmen I saw had their faces covered by hoods and scarves."

People hit the ground as panic and terror suddenly replaced the fun they were having while watching American metal band Eagles of Death Metal perform.

The four gunmen took hostages. But three of the four detonated the bombs in their suicide belts, blowing themselves and their hostages as the French special forces units attacked.

The survivors among the hostages described a horrific "bloodbath" as the shootings began.

One witness said: "It lasted at least, 10 or 15 minutes. They reloaded their weapons, they were well equipped. They reloaded three or four times and it lasted a good 10 minutes."

Another survivor said: "Everyone was cowering and running from the shots. It was chaos—there were so many people. Then 20 to 30 shots were fired, they fired randomly.

"I was walking on bodies, there was blood everywhere. People were lying dead in street."

Thomas, 27, described "rivers of blood" as he rushed towards the exit. "The aim was to attack and kill. Every time someone moved, we heard shots," he said.

Dozens of survivors hid in the theatre balcony and then climbed onto the roof, escaping into a nearby apartment where they found refuge while waiting for hours for authorities to arrive and secure the area.

John, who was among those who climbed the roof to escape, mentioned one steward who bravely rushed to open a door amid the gunfire, allowing people to escape onto the roof.

He said: "Someone who knew the venue, a steward, opened a door to the balcony. There were several children on the upper floor, I had a kid and woman next to me. I was one of the first to get out, then we pulled people up one by one onto the metal roof—around 60 of us."

Auralie hid in a room in the concert hall for more than two hours. "We could hear everything going on. It was as though people were being tortured, butchered. It was a massacre," she said.

Daniel Psenny, a journalist at Le Monde who lives behind the concert hall, allowed the survivors to take shelter in his apartment as the massacre went on nearby.

He said: "I heard a noise, like firecrackers, and I told myself it was just in the film I was watching. But the noise was loud, so I went to the window. I saw men lying on the ground, blood...I realised it was something serious. I wondered what was going on. Everyone was running onto the street. I had images of 9/11 in my head," the Daily Express reported.