Two French police officers were injured in a shoot-out during a raid on a house in Toulouse on Wednesday to arrest suspects in the killings of three children and a rabbi at a Jewish school in southwest France this week, a police source said.

The source said the raid began at 3:00 a.m. local time (02:00 a.m. British Time) and was ongoing, but did not provide further details.

French news channel BFM TV said the suspects were linked to an Islamist group which it identified as Forsane Alizza. BFM said police were negotiating with a 24-year-old man inside the house.

Reuters witnesses at the scene heard several shots at about 0440 British Time.

Heavily armed police in bullet-proof vests and helmets cordoned off the residential area where the raid was taking place, in a leafy suburb close to the Ozar Hatorah Jewish school where Monday's shootings took place.

Emergency services were also at the scene, but there were no visible signs of an ongoing siege.

Authorities believe that the gunman in Monday's school shooting was the same person responsible for killing three soldiers of North African origin in two shootings last week in Toulouse and the nearby town of Montauban.

A third soldier, of Caribbean origin, remains in a coma.

The same Colt 45 handgun was used in all three attacks and in each case the gunman arrived on a Yamaha scooter with his face hidden by a motorcycle helmet.

The killings come just five weeks before the first round of France's presidential elections in which immigration and Islam have been major themes as President Nicolas Sarkozy seeks to win over voters from far-right leader Marine Le Pen.

(Reporting by Jean Decotte, Nicolas Bertin and John Irish; Writing by Daniel Flynn; Editing by Louise Ireland)