President Viktor Yushchenko on Saturday pledged to hold Ukraine's "first ever free and fair vote" for parliament next weekend.
Ukraine's 45 parties and blocs will run for the 450-seat Verkhovna Rada.
The pro-Russian party of Yushchenko's Orange Revolution rival, Viktor Yanukovych, is expected to win the most votes but not enough to form a government on its own.
Yushchenko's Our Ukraine party is fighting for second place with the bloc led by Yulia Tymoshenko, his former ally who was sacked as prime minister last year after an acrimonious split in the Orange Revolution camp.
Ukrainian prosecutors have already launched 18 criminal cases over violations of election legislation and over 30 relating to attacks on campaigners and other acts of hooliganism, the president said.