KABUL, Afghanistan  Evidence is mounting that fraud in last weekend’s parliamentary election was so widespread that it could affect the results in a third of provinces, calling into question the credibility of a vote that was an important test of the American and Afghan effort to build a stable and legitimate government.

The complaints to provincial election commissions have so far included video clips showing ballot stuffing; the strong-arming of election officials by candidates’ agents; and even the handcuffing and detention of election workers.

In some places, election officials themselves are alleged to have carried out the fraud; in others, government employees did, witnesses said. One video showed election officials and a candidate’s representatives haggling over the price of votes.

Many of the complaints have come from candidates and election officials, but were supported by Afghan and international election observers and diplomats. The fraud appeared to cut both for and against the government of President Hamid Karzai, much of it benefiting sometimes unsavory local power brokers.