"We are taking irregularities very seriously," he said.

One of the worst cases has been in Paghman, a district west of Kabul, which is the stronghold of Abdul Rab Rassoul Sayyaf, a wartime faction leader and ally of President Hamid Karzai. Ballot boxes from 95 polling stations in Paghman have been set aside for further inspection and 30 to 40 of those had been cleared for counting by Sunday, officials said.

The rest would be excluded from the count because of clear evidence of fraud, said a foreign observer who lacked permission to speak to reporters and asked not be identified.

Mr. Sayyaf is running for a seat in the Wolesi Jirga, or the lower house of Parliament, and is in fourth place with 2,105 votes. Only 20 percent of the results for Kabul have been tabulated so far, but he is nevertheless well placed to win one of the 33 seats in the province.

Mr. Erben said that there were no signs of countrywide efforts to defraud the Afghan people but that there had been local efforts. "I do not believe these irregularities in any way have affected the overall elections, but some of them have surely affected them locally," he said. Voters went to the polls Sept. 18 to choose representatives for Parliament from each province, and for members of provincial councils.

"If compared with other, similar, postconflict elections, I think that the level of irregularities that we are currently reviewing is extremely reasonable," Mr. Erben said at a news conference.