Preliminary results released on Monday from Afghanistan’s presidential election seemed to give credence to candidate Abdullah Abdullah’s claim that voter fraud had been committed to favor his rival, Ashraf Ghani.

Abdullah and Ghani emerged as the frontrunners from a first voting round in April. According to Afghanistan’s election commission, the former got 3.5 million votes in the second round last month against 4.5 million for Ghani.

The chairman of the commission cautioned that the results were preliminary and admitted that votes had been rigged. “We cannot ignore the technical problems and fraud during the election process,” said Ahmad Yousuf Nuristani. “Some governors and government officials were involved in fraud.”

Final results are due to be announced in two weeks’ time.

Abdullah’s campaign nevertheless immediately rejected the tally as invalid. A spokesman said, “We don’t accept the results which were announced today and we consider this as a coup against people’s votes.”

Abdullah, who previously challenged outgoing president Hamid Karzai in the 2009 election, had insisted the results should be delayed until all problematic polling stations were audited.

According to the preliminary results, two million more Afghans turned out to vote in the runoff than did in the first round — which seems unlikely, especially given the country’s ethnic composition and traditionally low turnout among Pashtuns, the largest ethnic group.

Ghani, a former finance minister and World Bank economist, is Pashtun. His vice presidential candidate, Abdul Rashid Dostum, is a former Uzbek warlord. The two carried the country’s majority Pashto and Uzbek provinces.

Abdullah, of mixed Pashtun and Tajik descent, draws most of his support from the north which is home to a variety of smaller ethnicities and tribes. The stronghold of the Northern Alliance that resisted Taliban rule, the north largely resents the Pashtuns for supporting the radical Islamists until they were toppled in a Western invasion in 2001.