French President Nicolas Sarkozy on Wednesday said the three paratroopers killed by a gunman who claimed to have links with al Qaeda were victims of a "terrorist execution".

The French president was speaking in Montauban in the afternoon while presiding over the national memorial ceremony for the three slain paratroopers at their barracks of the 17th Parachute Engineer Regiment.

The suspect by the name of Mohammed Merah, a French national of Algerian origin, had killed three French paratroops last week in two separate incidents and later on shot dead another four including three pupils in a Jewish school in Toulouse on Monday.

"A French soldier knows death and how to confront it," Sarkozy said, "the death our men met was not the one they had been prepared for. It was not the death on the battlefields, but a terrorist execution."

The suspect gunman had been besieged by police in his residence in the north part of the city of Toulouse since early morning. The president confirmed that the stand-off between the suspect and police continued in Toulouse, some 50 kilometres away from Montauban.

The suspect gunman told negotiators that he acted to punish France's army for its foreign interventions and to revenge the killing of Palestinian children.

French chief Prosecutor Francois Molins said the suspect gunman had planned another killing on Wednesday. He told the press conference in Toulouse that the gunman might surrender Wednesday night.