French police arrested two people on Tuesday in the hunt for accomplices of an Al-Qaeda-inspired gunman who went on a killing spree in March, a judicial source said.

The two men aged 29 and 30 were detained in southwest France, where gunman Mohamed Merah killed three soldiers, a rabbi and three Jewish children before he was shot dead by elite police forces besieging his home.

French Interior Minister Manuel Valls said on Monday he did not believe Merah had been a "lone wolf", but had received help from overseas and been radicalized in France.

One of the gunman's brothers, Abdelkader Merah, was arrested on the day police surrounded his brother's apartment in the city of Toulouse in March. He denies being an accomplice in the killings but remains in detention during what has been deemed an anti-terrorism inquiry.

France's top anti-terrorism judge said earlier this week it needs more robust local policing, better intelligence sharing and the ability to infiltrate small radical Islamist groups if it hopes to fight new security threats at home in the aftermath of the Merah affair.