KABUL- Afghan election returns on Tuesday put President Hamid Karzai on course for a first-round victory, but a watchdog that can veto the outcome said it had found clear and convincing evidence of fraud and ordered a partial recount.

The disputed results put Karzai and Afghan election officials on a collision course with an international community ever more doubtful of a poll it funded and sent troops to protect.

Western officials initially hailed the August 20 election as a successful milestone, because Taliban militants failed to scupper it. Those assessments have become more guarded as evidence of widespread fraud has mounted.

The partial recount ordered by a U.N.-backed watchdog could delay a final result for weeks or months, keeping Afghanistan in a prolonged state of political uncertainty.

With votes from 91.6 percent of polling stations counted, the Independent Election Commission (IEC) reported Karzai ahead with 54.1 percent of the vote to 28.3 for main rival Abdullah Abdullah, who accuses Karzai's team of large scale fraud.

It was the first time the commission had reported Karzai on course to exceed the 50 percent threshold needed to win outright and avoid a second round. The result makes it a near mathematical certainty that when the remaining votes are counted Karzai will have 50 percent -- unless ballots for him are thrown out.

A separate Electoral Complaints Commission (ECC), led by a Canadian and mainly appointed by the United Nations, has the power to do just that. It went public with accusations of fraud for the first time.

In the course of its investigations, the ECC has found clear and convincing evidence of fraud in a number of polling stations, the body said in a statement announcing it had ordered a partial recount.

Abdullah called the official tally a tragic joke and said it included hundreds of thousands of phony ballots cast at ghost polling stations that never opened on polling day. He told Reuters it could cost desperately-needed Western support.

It will be very difficult to justify the support of the outcome of an election, for which hundreds of millions of dollars have been spent and NATO soldiers have died, ... (if) fraud decides the outcome, not the will of the people.

NO WINNER YET

Diplomats are worried at the prospect of the U.N.-appointed ECC being obliged to either bless or overturn a Karzai victory. They have repeatedly tried to discourage the Afghan authorities from suggesting the election is over before complaints are heard.

There are no winners in this election until the complaints are fully investigated by the Electoral Complaints Commission and there is a partial recount as ordered by the ECC, said Aleem Siddique, a spokesman for the U.N. mission in Kabul.

U.S. ambassador Karl Eikenberry told reporters: We're looking to the IEC and Electoral Complaints Commission to rigorously carry out their legal mandate to count all votes and exclude all fraudulent votes.

The U.N.-backed ECC ordered the Afghan-led IEC to recount results from polling stations where one candidate received more than 95 percent of the vote or more than 600 votes were cast.

The IEC says it has already set aside results from more than 600 polling stations that it considers suspicious.
It removed some results from its Web site without explanation, including those from several villages where Karzai supposedly won every single vote, in some cases with exactly 400 or 500 votes cast at multiple polling stations.

The election muddle could further sap support for the war among Western countries who have sent 103,000 troops and have seen public opinion sour in recent months as violence worsens.

Earlier on Tuesday a suicide car bomber blew up his vehicle outside a NATO military base at Kabul's main airport killing three civilians, the capital's worst attack since the vote.

A Taliban spokesman claimed responsibility for the attack.

Four U.S. service members were killed in a complex attack in the east of the country, the U.S. military said.

Lieutenant General Mohammad Afzal, commander of Afghan troops in the area, said six members of the Afghan security forces were also killed and 18 wounded in that battle, which raged throughout the day in Kunar province near the Pakistani border.

The war has also generated fierce debate in Germany three weeks before an election there. Last week German troops called in a U.S. air strike last week that Afghan officials say killed scores of people, many of them civilians.

The NATO-led International Security Assistance Force (ISAF) announced the start of a formal investigation into the incident, led by a Canadian general. For the first time, the force said clearly on Tuesday it believed civilians had been killed.

Subsequent review has led ISAF to believe that along with insurgents, civilians also were killed and injured in the strike, it said in a statement.

Chancellor Angela Merkel rejected premature criticism of the air strike -- the deadliest incident involving German troops since World War Two -- and promised a full account.

For a graphic, click here

(Additional Reporting by Sayed Salahuddin, Hamid Shalizi and Akram Walizada; writing by Peter Graff; editing by Andrew Roche)

(For more Reuters coverage of Afghanistan and Pakistan, see: here)

Afghanistan