The man believed to be behind the murders of four people at a Jewish school in Toulouse on Monday is a 24-year-old with French citizenship.

According to French police, Mohammed Merah was already known to the authorities in connection with other crimes. Police said he has been monitored by French intelligence for some time. He is thought to be behind the murders of three paratroopers earlier this month.

He is said to be of Algerian descent and has claimed to be an "Islamist warrior" linked to al-Qaida. He has told police that he wants revenge both for French involvement in foreign wars and for the deaths of Palestinians.

According to French media, he has links to a now-banned French Islamist group; Forsane Alizza (Knights of Pride) and has visited Pakistan and Afghanistan in the past. A police source said he had been arrested while in the Taliban-stronghold of Kandahar, but on a common law matter.

"He claims to be a mujahedeen and to belong to al-Qaida," said Claude Gueant, the French interior minister. "This person has made trips to Afghanistan and Pakistan in the past...and says he belongs to Al-Qaida and says he wanted to avenge Palestinian children and to attack the French army."