Abdullah has accused Karzai, provincial governors and police of complicity in efforts to rig the election, Reuters reported.
Around 15,000 people joined the protest, according to police and Reuters witnesses. Some demonstrated their outrage by destroying posters of Karzai and shouting angry slogans against the president and the independent election commission.
"We want the mujahideen back. We don't want technocrats and slaves of Jews and Christians," said Badam Gul, a former mujahid.
"We want justice at any cost. There's fraud and that is unacceptable for us. We will fight for our right until the last drop of blood in our body." The march was largely peaceful and well coordinated by its organisers. Water was distributed to protesters and organisers formed a protective cordon around sensitive locations like the Serena Hotel, where many top Afghan and foreign officials stay.
Most of the protesters dispersed later in the day.
Adding to the danger of electoral impasse for Afghanistan, an agreement with Washington to allow a smaller U.S. military presence after most foreign forces leave remains unsigned, as Karzai had wanted to leave it to his successor.
The top U.N. representative in Afghanistan warned of the risk of "a protracted confrontation with a danger of a slide into violence" in a briefing to the security council on Wednesday and urged Abdullah to return to the electoral process.
Abdullah has appealed to the United Nations to intervene to salvage the election, a solution that Karzai has also backed.