Preliminary tallies from Afghanistan's presidential election showed former foreign minister Abdullah Abdullah taking the lead in parts of Kabul.
The early result from the capital prompted claims of rigging by other frontrunners, although the weeks-long counting process means any predictions could be off.
The April 5 vote was meant to lead to the first democratic transfer of power in Afghan history as outgoing President Hamid Karzai prepares to step down after more than 12 years as head of state.
The United States plans to withdraw most of its troops by the end of 2014, a move that some fear could lead to further instability caused by the Taliban and from rivalry between factions in a country divided along ethnic and tribal fault lines.
"We are trying to start the process as soon as possible," Noor Mohammad Noor, a spokesman for the Independent Election Commission, said of the count, according to a report by the AFP news agency. "It's a long process ... It will take time."
If none of the eight candidates gets more than 50 percent, a runoff will have to be held, in late May at the earliest.
A tour of Kabul polling stations showed that Abdullah was firmly in the lead, confirming the popularity of the former anti-Soviet resistance fighter in the capital city.
However, although official preliminary results are not due till April 24, it looks increasingly likely Abdullah will face a runoff with Ashraf Ghani, an ex-World Bank official with a programme of radical economic reform.
Ghani, a former finance minister, should score well in the north as his running mate Abdul Rashid Dostum, an ethnic Uzbek, holds sway over much of the region.
According to informal preliminary tallies from around the country, ex-foreign minister Zalmai Rassoul may come a distant third.
He is believed to have Karzai's backing and is expected to do better in the ethnic Pashtun-dominated south, where the Karzai family has strengthened its influence over the years.
The Ghani and Rassoul camps both said they had received reports of violations and had submitted them to the Election Complaints Commission (ECC).
International and Afghan leaders have praised the Saturday vote as a success because of a higher-than-expected turnout - estimated at 60 percent of the 12 million eligible voters - as well as the failure of the Taliban to disrupt it significantly.