UNITED NATIONS (Reuters/AFP) - The International Atomic Energy Agency must investigate Irans newly-disclosed uranium enrichment plant and Tehran must take immediate steps to show its programme is peaceful, US Secretary of State Hillary Clinton said on Friday. Russia meanwhile, said Irans construction of the plant violated UN Security Council decisions and should be investigated immediately by the UN nuclear watchdog. This is now a clear challenge to the international community, Hillary told reporters in New York after Iran told the IAEA it had a second uranium enrichment plant under construction. The disclosure by Iran came just as six world powers and Iran prepare for rare talks on Oct. 1. The revelation of a secret nuclear plant near the holy city of Qom makes clear to those, who have either not formed an opinion or doubted the necessity of the dual track approach were pursuing, to work with us, she said. In Pittsburgh, a US official claimed that Irans hidden nuclear facility is the right size for the production of a small amount of uranium suitable for military use. Italy backed international criticism of the new Iranian atomic site and called on Tehran to disclose details of its nuclear programme. Italy supports the declaration of the leaders of the US, the UK and France on the new uranium enrichment plant in Iran, the Italian government said in a statement issued in Rome on Friday. Italy is opposed to Iran developing a nuclear military programme and calls on Tehran to clarify its nuclear programme in line with International Atomic Energy Agency demands, Italy said. Canadian Prime Minister Stephen Harper joined the US, Britain, France and Germany in demanding immediate access to a previously secret Iranian nuclear site. The Prime Minister echoed President Obamas concerns on todays news regarding nuclear proliferation in Iran, Harpers spokesman Dimitri Soudas told reporters on the sidelines of the Group of 20 summit in Pittsburgh. Harper supports whatever actions are necessary, he said. Russia is worried about Irans second uranium enrichment plant, Natalya Timakova, a spokeswoman for President Dmitry Medvedev, said Friday in Pittsburgh, promising a presidential statement later in the day. In a statement, Russias President Dmitry Medvedev urged Iran to cooperate fully with the UN nuclear watchdog in any probe of its new plant. Medvedev did not, however, raise the threat of sanctions, which Western powers have demanded if Tehran refuses to engage in dialogue on ending its uranium enrichment program, which they believe hides plans to build a bomb. Instead, the Russian leader said Iran should show convincing proof of its intention to develop nuclear energy solely for peaceful aims at talks with the international community on October 1. China has asked Iran to cooperate with the UN nuclear watchdog in any investigation, Chinese government spokesman Ma Zhao Xu said Friday. We have taken note that the Iranian side sent a letter to the IAEA, briefing the organisation on this matter, Ma told reporters on the sidelines of the Group of 20 summit of the worlds main economies in Pittsburgh. We have also taken note that the leaders of the US, UK and France made a statement on this. We are following the development of the situation. We hope that the IAEA will deal with the matter according to its terms of reference and mandate, Ma said, calling on Iran to work with the International Atomic Energy Agency in any investigation of the nuclear site. It is our hope that Iran will cooperate with the IAEA on this matter.