LONDON (AP) — Britain's cyber security chief says Russian hackers are targeting the country's telecommunications systems, media and energy networks.

Ciaran Martin's stark warning comes after Prime Minister Theresa May on Monday said Russia was "weaponizing information" and meddling in elections to undermine the international order.

Martin, in prepared remarks released before a speech on Wednesday, says "Russian interference, seen by the National Cyber Security Center over the past year, has included attacks on the U.K. media, telecommunications and energy sectors."

The Guardian newspaper on Wednesday reported that more than 400 Twitter accounts run from Russia published posts about Britain's departure from the European Union in an attempt to influence local politics. The Times of London reported that Russian accounts posted almost 45,000 Brexit messages in the final hours of last year's referendum.