Rio Tinto Group the world's third largest mining company rose in London trading last week by the most in almost two months after the Financial Times Alphaville blog said that BHP Billiton Ltd may increase its offer.

FT Alphaville without saying where it got the information said that BHP may boost its bid to four shares for every one of Rio's. it said that Australian government gave permission for a larger Chinese stake in Rio.

Ms Christina Mills a spokeswoman of Rio and Ms Tracey Whitehead a BHP spokeswoman in New York both declined to comment.

Rio rejected a sweetened offer of 3.4 BHP shares for each of its shares on February 6th 2008 saying it undervalued the company.