By Timothy Heritage and Maria Tsvetkova MOSCOW (Reuters) – Victories are hard to come by for Vladimir Putin’s opponents, activists are jailed, protests draw dwindling crowds, but on Friday they celebrated a minor triumph by briefly knocking out the Kremlin website. To red faces in the Kremlin and government, the central bank’s site was also brought down by a cyber attack and the Foreign Ministry suffered similar problems. “A powerful cyber attack is under way on the (Kremlin) site,” a spokeswoman for the Russian president’s press service said by telephone as security experts struggled to curtail disruption. A Kremlin source told Itar-Tass news agency there was no link with “the events in Ukraine”, referring to the standoff with the West over Crimea, which votes on Sunday on unification with Russia.