ZURICH (Reuters) - Three Kazakh weightlifters have been stripped of the gold medals they won at the 2012 London Olympics after failing doping tests in the re-analysis of samples, the International Olympic Committee said on Thursday.

The three were Zulfiya Chinshanlo in the women's 53kg category, Maiya Maneza in the women's 63kg and Svetlana Podobedova, who competed in the 75kg event.

They were among eight athletes disqualified from the Games on Thursday as part of the IOC's re-testing of samples.

A total of 98 samples have come back as positive for banned substances in re-analysis from the 2008 and 2012 Games as the IOC attempted to root out cheats and stop them from going to this year's Rio de Janeiro Olympics.

The other five athletes were Belarussian weightlifters Marina Shkermankova, who won bronze in the 69kg category, Dzina Sazanavets and Yauheni Zharnasek as well as Russian pole vaulter Dmitry Starodubtsev and hammer thrower Kirill Ikonnikov.

All eight tested positive for turinabol or stanozolo, anabolic steroids that boost performances or speed up recovery from injury.

On Wednesday the IOC announced nine other positive cases from the 2008 Beijing Olympics, including six medallists, all of whom also tested positive for steroids.

The IOC stores samples for a decade to test with newer methods or to analyze performance-enhancing substances that have yet to be identified.

The vast majority of the 98 athletes who have tested positive are from Eastern European countries or Russia.

(Writing by Brian Homewood and Karolos Grohmann; Editing by Michael Shields)