U.S. President George W. Bush on Saturday congratulated Kazakhstan\'s president, Nursultan Nazarbayev, on his re-election and urged him to investigate allegations of voting irregularities. Nazarbayev told Bush that his government was prepared to investigate the charges, the White House said. Nazarbayev won re-election by a landslide on Monday in the central Asian state, but international observers branded the vote flawed, citing ballot box stuffing and the intimidation of opposition campaigners.Blair Jones, a White House spokesman, said Bush called Nazarbayev to \"congratulate him on his re-election and to highlight the importance of continued democratic reform in Kazakhstan.\" \"Allegations of irregularities in the election were noted and the (U.S.) president stressed the importance of Kazakhstan investigating the facts related to these allegations,\" Jones said. \"Nazarbayev said Kazakhstan is prepared to investigate the facts provided to them.\" The landslide win for Nazarbayev, in power since 1989, means he will rule the Central Asian state for another seven years. Under his rule, Kazakhstan reformed its economy and is set to become one of the world\'s top 10 oil producers in the next decade as it develops new oil fields in the Caspian Sea. (Reuters)