Ukraine's opposition presidential candidate, Viktor Yushchenko, has urged his supporters to keep up the pressure for a free and fair re-run Sunday as his rival, Prime Minister Viktor Yanukovych, warned of the possibility of further unrest.  The competing rallies come just four days before the new election ordered by Ukraine's Supreme Court.

Tens-of-thousands of Yushchenko supporters, decked out in the opposition campaign's trademark color orange, have flooded back into Kiev's Central Independence Square to demand that the re-run of the presidential election on Sunday be free and fair.

The square, or Maidan as it is known locally, has become the focal point of the opposition movement and had largely returned to normal in the past two weeks after Ukraine's Supreme Court overturned the earlier election results declaring Prime Minister Viktor Yanukovych the winner.  The Court found for the opposition's claim of massive voter manipulation and fraud in the second-round run-off vote and ordered the re-run presidential vote for this weekend.

Mr. Yushchenko, who has since taken the lead in the presidential campaign, returned to Independence Square Wednesday night to urge his supporters to keep up their street protests in order to protect their votes.  The opposition candidate, who was poisoned during the course of the campaign, said the road had not been easy and that many challenges remain.

Mr. Yushchenko says his supporters should remain in Kiev's Central Independence Square until the opposition can celebrate an official election victory.  He also commended his followers for, in his words, "changing Ukraine peacefully."

He said the first priority of his administration, if elected president, would be to integrate Ukraine into the European community of democratic nations.  At the same time, he said relations with Russia would always be an important priority.

Mr. Yushchenko also vowed to unite Ukraine, which at one point during the electoral stand-off threatened to split between the pro-reform west and the regions in the east that favor pro-Russia Prime Minister Yanukovych.

About 2000 Yanukovych supporters gathered in the central Ukrainian city of Kirovograd Wednesday for a competing rally to support their candidate. 

Mr. Yanukovych told his supporters that the 17 days of opposition rallies on Kiev's Independence Square were very dangerous for Ukraine.  He warned of the possibility of renewed violence during the re-run and said he would not like to see blood spilled over an election.

Mr. Yanukovych has urged his competitor to join him in accepting the outcome of Sunday's re-run election, whatever it may be.  He has also said both leaders should host a national reconciliation forum to ensure Ukraine's future unity, an appeal ignored by Mr. Yushchenko, who is widely expected to win the re-run, if it is free and fair.

More than 12,000  foreign and local observers are descending upon Ukraine to monitor the election on Sunday.