Toulouse, Mar 23 (Reuters): Eight people are being held captive in a supermarket in the south-western France town of Trebes, a police source said on Friday, adding that the hostage-taker had shot at a police officer.

BFM TV said the hostage-taker has claimed allegiance to Islamic State.

Counter-terrorism prosecutors have opened an investigation into security incident underway in southern France, a source in the Paris prosecutor's office said.

"I can confirm to you that the anti-terrorism division of the Paris prosecutors has taken up the case," the source said after police said eight people were being held hostage in a supermarket in southern France.

The local prefecture confirmed the hostage-taking at the Super U supermarket but did not confirm the Islamic State allegiance.

Earlier, France's Interior Ministry had said security officials were carrying out an operation at a supermarket in southern France, but gave no details.

The UNSA police union also said on Twitter a police operation was underway after an individual had earlier shot at four officers in the Carcassone region injuring one of them.