KIEV, Ukraine — Ukraine's Prime Minister Yulia Tymoshenko, apparently narrowly beaten in last week's presidential vote, ended six days of silence on a defiant note Saturday, saying the vote had been rigged and she would challenge the result in court. Preliminary results from the Feb. 7 ballot gave her rival, opposition leader Viktor Yanukovych, a lead of just 3.5 percentage points. International observers called the elections free and fair, but no official winner has been declared, and Tymoshenko has refused to concede defeat. She said Saturday she had evidence of fraud and would fight the result, for which the final...