KABUL, Afghanistan - With political tensions running high in advance of President Hamid Karzai's expected announcement this week of his new cabinet, a suicide car bomber struck in the heart of Afghanistan's capital yesterday, killing eight people and injuring more than 40.

Officials said the target may have been former Vice President Ahmad Zia Massoud, whose house was badly damaged in the attack.

Massoud is the brother of Ahmad Shah Massoud, the much-revered leader of the anti-Taliban resistance who was assassinated in 2001 just before the Sept. 11 attacks on the United States.

Massoud had left the residence shortly before the explosion and was uninjured, said an aide. Two of his bodyguards were among the dead.

Like many previous attackers, the bomber managed to penetrate a wealthy area of the capital where tight security measures are in place.

The ease with which attackers are able to gain access to high-security zones has in the past raised suspicion of collusion between the Taliban and Afghan security forces.

The blast, which echoed across Kabul and sent black plumes of smoke billowing into the air, brought traffic in the city center nearly to a standstill. Witnesses said ambulances were not on the scene right away, so neighbors and passersby helped the injured as best they could.

"There were no police; everybody was helping carry the wounded away themselves," said Farhad Yaftali, a construction company worker.

Aides to Massoud said they were certain he was the intended target, although authorities initially believed the bomber might have been trying to approach a hotel several hundred yards away that is frequented by foreigners and diplomats.

A spokesman for Afghanistan's Interior Ministry, Zemeri Bashary, said the eight dead included four women. He said more than three dozen people were hurt.

The attack took place as senior Afghan officials were convening about a mile and a half away to discuss measures to combat corruption, a topic of keen interest to Western governments.

In a reminder of the continuing cost of the conflict as the United States prepares to increase its troop commitment by 30,000, military officials yesterday disclosed the death of a U.S. serviceman a day earlier in a roadside bombing in southern Afghanistan, and reported the deaths of two British and two Afghan soldiers, also in the south.

Karzai's ministerial choices, which may be known as early as today, are being watched as a sign of whether the Afghan leader intends to follow through on pledges to rein in rampant corruption.

In his speech to the senior officials, Karzai declared that "our duty is to tackle corruption in government, whether trifling or very large-scale."

But he also referred to an abundance of "Western propaganda" on the subject and defended the mayor of Kabul, who recently was convicted on corruption charges, as a "clean" politician.

Also yesterday, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said in Kabul that the vast majority of troops in the surge ordered by President Obama should be in Afghanistan by August, as scheduled, the Associated Press reported.

On Monday, Lt. Gen. David Rodriguez, the second-highest ranking U.S. general in Afghanistan, had said the escalation of American troops would take longer than expected, possibly as long as 11 months, citing logistical challenges.