PARIS (AFP) - A 26-year-old man taken hostage Friday by the two gunmen who carried out the Charlie Hebdo massacre gave them the slip as commandos launched an assault that killed the Islamist brothers, a security source said.

The man, whom he did not name, emerged "safe and sound" from the printing firm in the village of Dammartin-en-Goele, just north-east of Paris, where the gunmen had holed up, the official told AFP.

He had escaped from them inside the building and locked himself in a room, just as they were heading outside with their automatic assault rifles in hand.

The two brothers, Cherif and Said Kouachi, were cut down outside the building as they tried to shoot their way past police.

Earlier, a worker at the printing firm recounted how he had met the hostage and the two brothers coming in, and how they had presented themselves as police.

The worker had shaken hands with the hostage and one of the gunmen before realising they were the criminals being hunted by France's police. He was allowed to leave.

The security source told AFP that during the assault on the CTD printworks one police commando was "slightly hurt" but did not elaborate.