At least six people have died and over a hundred were injured when a packed French intercity train derailed and crashed at high speed into a station outside Paris.

The French railway company SNCF said the train travelling from Paris to Limoges was carrying 385 passengers when it derailed at 5.15pm on Friday at Brétigny-sur-Orge in Essonne, 20km south of Paris.

Four of the train's seven carriages ploughed into a crowded platform at rush hour on one of the busiest days of the year for holiday getaways.

Security services have been working on the wreckage where passengers are believed to be trapped in mangled carriages, which were lying on their side.

The French president François Hollande, visiting the scene, said six people were killed and 22 were seriously injured, including one who was in a critical condition. The prefect's office in Essonne said a total of 180 people were injured. Hollande said three inquiries had been launched into what caused the derailment.

Michael Lesaunier, the owner of a cafe beside the busy suburban station told iTele: "The train approached very, very fast, knocking out everything in its path. It was rush hour, the platform was full."

He added that the passengers he had seen were very shocked and talking of serious injuries.

Boris Berson, a passenger travelling in one of the carriages that did not derail, said the passengers in his unaffected carriage were shaken and "did not know what was going on".

El Mehdi Bazgua, 19, who saw the derailment from the window of a different RERC local suburban train, told Le Parisien website: "I heard a massive noise and saw a cloud of sand that covered everything. I saw stones and wires on the ground. Then the dust lifted … We saw the first injured. I saw a man with an open head wound. Lots of people were cut. Lots of train passengers were blocked under the train."

He had heard of very bad injuries and said a lot of passengers on his train were crying. One of the wounded passengers asked observers not to film the accident.

Rescue workers assist victims at the scene of the derailment. Photograph: Etienne Laurent/EPA

Several witnesses described the train as appearing to "split in two". One witness told Europe 1 radio of a scene of chaos and panic at the station where he said the derailed carriages were "crushed".

The Socialist mayor of Brétigny, Bernard Decaux, told Le Parisien: "Three carriages were tangled up one behind the other", with a fourth lying on its side. He added: "I have no idea of the number of casualties, I've just been told it risks being very heavy. There are people injured by ballast."

He said "Everyone was running in all directions. It was panic. It was an apocalyptic sight."

At the scene, Guillaume Pepy, head of SNCF, in tears in front of the TV cameras, talked of a "rail catastrophe".

Hospitals in Paris have been on emergency alert to treat serious injuries, including from electrocution. As hundreds of emergency staff worked on the wreckage, the cause of the derailment has not yet become fully clear.

The train had left Paris-Austerlitz station at 4.53pm and was scheduled to pass through Brétigny station at high speed without stopping on its way to Limoges at 8.05pm. But carriages three and four derailed and careered into the train platform, dragging others behind them.