By Adrian Croft and Peter Apps BRUSSELS/LONDON (Reuters) – Hackers brought down several public NATO websites, the alliance said on Sunday, in what appeared to be the latest escalation in cyberspace over growing tensions over Crimea. The Western military alliances spokeswoman, Oana Lungescu, said on social networking site Twitter that cyber attacks, which began on Saturday evening, continued on Sunday, although most services had now been restored. At no time was there any risk to our classified networks, another NATO official said. NATOs main public website (www.nato.int), which carried a statement by Secretary-General Anders Fogh Rasmussen saying that Sundays referendum on Crimeas status would violate international law and lack legitimacy, worked intermittently.