Supporters of presidential candidate Abdullah Abdullah tear up a photo of outgoing president Hamid Karzai.
Preliminary results on Monday said alternative contender Ashraf Ghani finished first with over 56 percent of the vote.
But Adbullah's supporters say the vote was rigged, with Karzai helping to swing the vote in favour of his competitor.
(SOUNDBITE) (Dari) AFGHAN PRESIDENTIAL CANDIDATE, ABDULLAH ABDULLAH SAYING:
"We are the winner of this round of elections without any doubt. We will not allow the fraudulent government to rule this country for even one day without any doubt."
Abdullah is now facing increasing calls from his supporters to form a parallel cabinet to unilaterally assert his own rule.
If he does, it would be a dangerous move that would further fracture the fragile country
So far Abdullah has asked his supporters to be patient.