Police in southern France have arrested four women and a girl as part of an anti-terrorist investigation into a suspected attack plot targeting the city of Montpellier.

A police official in the Herault region confirmed the overnight arrests in the city of Beziers, and said the DGSI domestic intelligence service and national anti-terrorist prosecutor’s office are handling the investigation.

Investigators centred on an 18-year-old woman living in a housing project in Beziers who is suspected of plotting an attack targeting nearby Montpellier, according to mayor Robert Menard. The 18-year-old’s mother and three sisters were also arrested, including one who is a minor, he said.

The 18-year-old had “boasted” to neighbours about watching Islamic State videos, Mr Menard told The Associated Press, though he said he did not know whether she or her family had been on authorities’ radar for radicalism.

Mr Menard, who was alerted by police to the operation, said he spoke with rattled neighbours at the scene.

“They’re horrified. They fear it gives a bad image of this neighbourhood, and the Muslim community here,” he said.