South Africa and the United States are among at least five countries that filed initial paperwork required ahead of any potential 2020 Olympic bids.

Eat an orange. Wear a face mask. Train elsewhere and fly in at the last possible moment to compete. These are some of the strategies suggested for Olympic athletes planning to compete in Beijing, where a thick cloud of smog often blankets one of the world's most polluted cities.

Film director Steven Spielberg and actress Mia Farrow joined activists worldwide on Tuesday in using the Olympics as a backdrop to address human rights concerns, urging Beijing to exert political leverage on Sudan's government to help end the crisis in Darfur.

United States sprinter Marion Jones handed over her five medals from the 2000 Olympic Games to an official of the United States Anti-Doping Agency (Usada) on Monday. Once the world's fastest woman, Jones was hailed as the queen of the Sydney Games, where she won three gold medals, including the 100m, as well as two bronze medals.