Russia voiced skepticism Tuesday about Iran's announcement of a dramatic expansion of its uranium enrichment effort, saying it had not received confirmation of the claim. Iran said Monday it has begun operating 3,000 centrifuges - nearly 10 times the previously known number - in defiance of UN demands that it halt its nuclear program or face increased sanctions. Russia was unaware, however, of "any recent technological breakthroughs in the Iranian nuclear program that would change the format of its enrichment effort," Foreign Ministry spokesman Mikhail Kamynin said in a statement. "We haven't got a confirmation yet that they have actually begun uranium enrichment at the new cascades," Foreign Minister Sergey Lavrov told reporters, according to the Interfax, ITAR-Tass and RIA Novosti news agencies. The European Union also called on Iran to live up to international demands to halt its nuclear program and return to negotiations. "Iran should comply with its obligations under the nuclear nonproliferation treaty and should implement the United Nations Security Council resolutions," said EU spokeswoman Christiane Hohmann. In a similar statement made on Tuesday, the French foreign minister denounced Iran's announcement as a "bad sign" and urged Iran to respect UN demands to halt such activity. "Once again I urge Iran to respect the Security Council resolutions that require the suspension of all sensitive nuclear activities," Philippe Douste-Blazy said. But while expressing concern about the announcement, French Foreign Ministry spokesman Jean-Baptiste Mattei was cautious about whether Iran had the means to follow through. "There are announcements, and then there is technological reality," he said. Meanwhile, two UN inspectors have arrived in Iran to visit its uranium enrichment plant, the authorities said Tuesday. "Two inspectors from the International Atomic Energy Agency arrived in Teheran early Tuesday," the official Islamic Republic News Agency reported. An official of Iran's Atomic Energy Organization confirmed their arrival, and said the visit was "routine." US experts say 3,000 centrifuges are, in theory, enough to produce a nuclear weapon, perhaps within a year. But they doubted Iran had so many up and running, a difficult technical feat given the country's spotty success with a much smaller number.