A retired US marine who has been detained by Russia for alleged spying was visiting Moscow for the wedding of a former fellow marine and is innocent of the espionage charges against him, his family said.Paul Whelan had been staying with the wedding party at Moscow's Metropol hotel when he went missing, his brother, David, said."His innocence is undoubted and we trust that his rights will be respected," Whelan's family said in a statement released on Twitter on Tuesday.Russia's FSB state security service said Whelan had been detained on Friday, but it gave no details of his alleged espionage activities. Espionage can carry a prison sentence of between 10 and 20 years under Russian law.A US State Department representative said Russia had notified it that a US citizen had been detained and it expected Moscow to allow consular access to him."Russia's obligations under the Vienna Convention require them to provide consular access. We have requested this access and expect Russian authorities to provide it," the representative said, without providing details of the American's identity or the reasons behind his detention.