NEW : ' Vote-counting begins late Wednesday . The first round of voting will be held on Saturday and the second round is scheduled for Sunday. Partial results are due early Thursday with full results due by Monday . NEW : The head of the election commission says the vote was `` free and fair '' President Robert Mugabe 's main challenger is PM Morgan Tsvangirai .
NEW : Vote-counting begins late Wednesday . The first round of voting will be held on Saturday and the second round is scheduled for Sunday. Partial results are due early Thursday with full results due by Monday . NEW : The head of the election commission says the vote was `` free and fair '' President Robert Mugabe 's main challenger is PM Morgan Tsvangirai .