Thousands of Ukrainian opposition activists have rallied in the capital, Kyiv, to protest the arrest and jailing of their leader, former prime minister Yulia Tymoshenko, as the country marks its 20th anniversary of independence from the Soviet Union.

The activists gathered Wednesday near a monument to national poet Taras Shevchenko in central Kyiv and tried to march through the city, but police blocked their path. The protesters denounced Tymoshenko's arrest earlier this month on charges of contempt of court. She is on trial for alleged abuse of office when she signed a gas deal with Russia in 2009 while serving as prime minister.

A Ukrainian court had banned opposition groups from holding rallies in most of the capital on the independence anniversary.

Ukrainian President Viktor Yanukovych attended ceremonies in Kyiv to mark the occasion, but the festivities were low-key as the government tries to cut back on spending to reduce its budget deficit.

Speaking ahead of the anniversary, Mr. Yanukovych said he expects to complete negotiations with the European Union on a political association agreement and a free trade deal by the end of this year. He said Ukraine has made an “irreversible” choice to adopt what he called the European social model, while maintaining historic ties with Russia, which provides crucial supplies of natural gas.

Mr. Yanukovych defeated Ms. Tymoshenko in a close presidential election last year. Ms. Tymoshenko says her trial is part of a political vendetta against her by the president. A conviction would make her ineligible to run for office in parliamentary elections next year and the next presidential contest in 2015.