ABC correspondent Emma Griffiths reports. ANNIE WHITE: Authorities in Uzbekistan have sealed off part of the eastern city of Andijon, where troops fired on a crowd of demonstrators killing as many as 500 people. Thousands of Uzbeks are now trying to leave the country, massing on the neighbouring Kyrgyzstan border. The Uzbekistan Government claims to have the situation under control, but some observers are predicting more widespread instability in the former Soviet state. There are also calls for the United States to rein in its central Asian ally. ABC correspondent Emma Griffiths reports. EMMA GRIFFITHS: The border town of Korasuv...