Updated

An Afghan election official said Wednesday that national elections held last weekend were a success in terms of turnout and enthusiasm, but he cautioned that there may have been significant fraud.

Millions of Afghans voted for a new president and provincial councils on Saturday in what promises to be the country's first democratic transfer of power. With eight candidates including three front-runners, it will be hard for anybody to gain a majority needed for an outright win, and most expect the top two vote-getters to face a runoff in late May.

Widespread fraud marred the 2009 presidential elections and authorities took precautions to prevent that from recurring. Still, the electoral complaints commission said it received more than 3,000 complaints about irregularities and promised to invalidate all votes deemed fraudulent.

"Election fraud did take place and it might not have been a small amount," said Abdul Satar Sadaat, the head of the complaints commission.

More than 7 million Afghans defied Taliban threats to vote. President Hamid Karzai, who has led the country since the Taliban were ousted in 2001, is constitutionally barred from a third term.

With combat forces from the U.S.-led coalition winding down a 13-year presence, the country's new leader will find an altered landscape.

The three main contenders -- Abdullah Abdullah, who was Karzai's main rival in the disputed 2009 vote,  Ashraf Ghani Ahmadzai, an academic and former World Bank official, and former Foreign Minister Zalmai Rassoul -- all have promised to sign a security agreement with the Americans to allow thousands of foreign forces to remain in Afghanistan in a mainly training and advisory role.

Afghans have widely hailed the elections as a success, and several ceremonies have been held to praise government security forces for securing voters and polling centers without any major attacks. A series of high-profile attacks in the weeks before Saturday's vote had raised fears there would be more on election day.

"Despite the challenges and problems that existed in this election, the widespread participation of voters was a good achievement compared to the previous election," said the head of the Independent Election Commission that oversaw the vote, chairman Ahmad Yousuf Nouristani.

Electoral officials have urged patience, saying officials continued to log complaints and tally ballots. Some candidate forecasts and partial results are expected in the coming days. Noor Mohammad Noor, a spokesman for the Independent Election Commission, said preliminary results were due April 24 and final results will be announced May 14.

Authorities also reported more violence on Wednesday.

Two bombs struck separate targets in Khost Wednesday morning, killing one policeman and wounding eight other people, provincial government spokesman Mubariz Mohammed Zadran said.

A roadside bomb, apparently planted on election day, also exploded as a civilian car drove over it on Tuesday, killing two civilians and wounding six others in Ghazni province, the province's deputy governor Mohammad Ali Ahmadi said. Explosives planted elsewhere in Ghazni also killed one child and wounded two others as they were playing nearby, Ahmadi said.