LYON, France (Reuters) – Attackers set fire to vehicles beneath a housing complex for police and their families in a suburb of Grenoble, eastern France, on Thursday.

Police said a fence around the building was closed off in an apparent attempt to prevent residents escaping and rescuers getting in, but all 24 people inside escaped unharmed.

Nobody claimed responsibility for the assault, which was the latest in a series of arson attacks against police and police vehicles.

“Attacks like this can be tantamount to terrorism,” Grenoble prosecutor Jean-Yves Coquillat told reporters, adding that the method used was similar to other recent attacks by far-left groups.

Last month, such a group claimed responsibility for an arson attack on a police building in Grenoble that destroyed a warehouse and several cars.

The group said the fire was a protest against the trial of nine far-left activists accused of firebombing police in an assault on two officers in Paris in May 2016 that was caught on camera.

Last month, five police cars were set on fire in Limoges, central France.

French police are on high alert after a series of Islamic State-inspired attacks that have killed more than 240 people in the past three years.

Aside from the Islamist threat, far-left and far-right militancy has also not let up. Police this month arrested 10 far-right militants suspected of planning attacks on mosques and politicians.