Two anarchist groups claimed responsibility for a massive power cut that hit the French Riviera over the weekend, saying the sabotage was aimed at "disrupting" the Cannes Film Festival. Power was lost for five hours on the final day of the festival on Saturday, knocking out traffic lights and ATMs and forcing organisers to use back-up generators. Local officials said asuspected arson attackon a substation and vandalism of an electricity pylon were the causes. The headquarters of the festival switched to a backup power supply. Full power was subsequently restored, allowing Saturday night's closing ceremony to go ahead as planned. In an anonymous letter published online on Sunday, the two groups said they were behind the massive outage. "The aim of the action was not only to disruptthe festival, but also to deprive all industrial establishments of electricity," the anarchist groups reportedly wrote in their letter. "We're not on a film set, but 'cut!' seemed to sum up our desire to turn off this deadly system," they added, according to a police source. On Saturday, Damien Savarzeix, the public prosecutor in Grasse, said that three of the four pillars of a pylon on the high-voltage line in Villeneuve-Loubet, which supplies power to part of the area, including Cannes, "were sawn off" in a "malicious act". Electricity workers then switched off the line to allow the work to be carried out, indirectly causing a power cut that left 160,000 homes without electricity throughout the day. Following the Cannes incident, a blaze then hit an electricity transformer in the western part of the city of Nice overnight on Saturday, knocking out power to 45,000 homes in the city and the surrounding region, the offices of the mayor and local prosecutors said. "I vigorously condemn these criminal acts hitting our country," Nice Mayor Christian Estrosi said on X. "In the coming days, we are reinforcing the (security camera) network around the city's strategic electric sites." Power was restored around dawn, officials and the Enedis grid company said. At Cannes, the Palme d'Or went to A Simple Accident directed by Jafar Panahi, an Iranian filmmaker who was barred from leaving the state in 2018 when he earned a best screenplay prize. Mr Panahi has been imprisoned several times and went on a hunger strike in 2023 amid a state ban on his filmmaking. French foreign minister Jean-Noel Barrot said his Cannes award was a further "gesture of resistanceagainst the Iranian regime's oppression". On Sunday, Iran summoned the French charge d'affaires in Tehran over what it called the minister's "insulting remarks and unfounded allegations". Broaden your horizons with award-winning British journalism. Try The Telegraph free for 1 month with unlimited access to our award-winning website, exclusive app, money-saving offers and more.