KABUL (Reuters) – A suicide car bomber blew up his vehicle outside a NATO military base at Kabul’s main airport on Tuesday killing at least three civilians, in the biggest attack in the Afghan capital since last month’s presidential election.

The attack was a further demonstration of deteriorating security at a time when violence is at its worst, an unresolved election has put the country’s political future in doubt and Western popular support for the war is rapidly eroding.

The head of criminal investigations for Kabul police, Abdul Ghafar Sayedzada, said three civilians were killed and six wounded in the airport attack.

No foreign troops were killed, said Captain Elizabeth Mathias, a media officer for the NATO-led force. Four were lightly injured.

A shopkeeper who witnessed the blast told Reuters the suicide bomber detonated his explosives close to one of the entrances of the military side of the airport.

“A suicide bomber in a ‘Surf’ car (off-road vehicle) exploded himself near the main gate (guarded) by Nepali guards,” said the shopkeeper, Izmarai, who uses only one name.

“Another man was riding his bicycle and fell to the ground. The police carried another wounded person away,” he said.

Huge flames could be seen rising from the blast site and the wail of sirens could be heard several kilometers from the civil-military airport, which has seen a series of Taliban rocket attacks and a suicide strike in the past.

A Taliban spokesman said by phone from an undisclosed location the militants were responsible for the blast, targeting Western forces. The attack came less than a month after a suicide car bomber struck the NATO headquarters entrance in Kabul, killing at least seven people and wounding 100.

U.S. PUBLIC SUPPORT FADES

Increased violence in Afghanistan has sapped public support for the war in the United States, which now has about 65,000 troops among the 103,000 foreign troops there.

The war has also become a matter of major controversy in Germany, weeks before a general election, after German troops called in a U.S. air strike last week that Afghan officials say killed scores of people, many of them civilians.

Karzai called the decision to bomb hijacked fuel trucks in the north of the country a major “error of judgment.”

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.

German Defense Secretary Franz Josef Jung has defied calls to resign over the incident — the deadliest involving German troops since World War Two. Jung has said the attack was necessary and his information indicated only Taliban fighters were killed.

Chancellor Angela Merkel was to go before parliament later on Tuesday to explain the government’s strategy.

The incident last Friday is a test for the new NATO commander, General Stanley McChrystal, who took charge of the force three months ago vowing to protect Afghan civilians. He has gone on television to reassure Afghans he is investigating.

FRAUD CHARGES CLOUD ELECTION RESULTS

Fraud accusations have meanwhile eroded confidence in the outcome of the August 20 election. Officials said they were finishing up the long-delayed count of results, and were due to publish an almost-complete tally later on Tuesday.

The last announced figures, with 74 percent of polling stations counted, showed President Hamid Karzai falling just shy of the 50 percent needed to avoid a run-off — so close the final outcome could be delayed for weeks more by fraud investigations.

Most remaining votes are in the south, where results so far have given Karzai strong support but his main challenger, Abdullah Abdullah, says ballots were stuffed on a huge scale.

The Independent Election Commission says it has already set aside results from more than 400 polling stations because of fraud concerns. A spokesman said that amounted to about 200,000 votes, equivalent to about 4.5 percent of votes tallied so far.

Western officials initially hailed the election because Taliban fighters failed to scupper it, but as fraud allegations have mounted those assessments have become more guarded.

After the election commission issues complete preliminary results — expected this week — the Electoral Complaints Commission, a separate fraud watchdog mainly appointed by the United Nations, can exclude ballots it thinks were fake.