Ukraine's Supreme Court today invalidated the official results of the disputed presidential run-off election and ruled that a repeat vote must be held.
Presiding Judge Anatoly Yarema said the rerun should be held by 26 December.
The court issued its verdict in response to an appeal by opposition leader Viktor Yushchenko, who asked the court to cancel results of the 21 November run-off. He said it had been rigged in favour of Prime Minister Viktor Yanukovych.
Yushchenko has pushed for a quick rerun of the run-off, saying it may come as early as 19 December. He has rejected outgoing President Leonid Kuchma's call for a completely new election which was widely seen as an attempt to field a new candidate more popular than Yanukovych.
Tens of thousands of opposition protesters who had massed in Kiev in anticipation of the decision cheered, waving blue-and-yellow Ukrainian and orange Yushchenko flags and chanting "Yushchenko! Yushchenko!" The crackle of fireworks could be heard in the distance.