World Cup fans should be on alert for Russian spies targeting them for information and blackmail operations, a European spy chief has warned.

Mikk Marran, head of the Estonian foreign intelligence service, advised fans, footballers and any other foreigners visiting Russia in June and July for the tournament to keep phones, laptops and other electronic devices with them at all times or not to bring them at all.

He also said that strangers who struck up conversations in bars and other public places could be undercover agents, trying to establish friendships that could be exploited. “People are giving out a lot of information when they travel to Russia: names, addresses, social security numbers. That data is installed in systems of the Russian special services,” Mr