A top member of President Hamid Karzai's Cabinet threatened to quit after a car bomb targeted him, killing five people, in the latest Taliban attempt to destabilize Afghanistan's struggling government.

Shortly after the bombing Sunday in the western city of Herat, Energy Minister Ismail Khan railed against the dramatic rise in violence in Afghanistan, saying that thousands of new refugees are seeking shelter in Herat because of militant attacks in outlying districts. Five civilians died in the failed assassination attempt, police said.

Two days ago, Khan said, a young man was hanged by militants only a couple miles (kilometers) outside a NATO base and Afghan government center. Kidnappings of wealthy family members are on the rise, including the abduction of girls, he said.

Khan said government security agents had warned him that insurgents planned to target him. Two earlier assassination attempts had been foiled, he said.

"Very clearly I want to say that if the government does not form a clear strategy to bring peace and security, and the situation continues like this, I will not participate in the Cabinet anymore," Khan said.

Taliban assassination attempts against Afghan officials have intensified this year, with more than 100 officials and pro-government tribal elders attacked — half of them fatally. Echoing a strategy of insurgents in Iraq, the targeted violence undermines the weak government and drives educated and competent Afghans away from official posts.

The convoy carrying Khan, a powerbroker in Herat and former governor of that western province, was headed to the airport when a suicide car bomb exploded outside a high school, said Raouf Ahmadi, a police spokesman. Khan said five civilians died and 17 people were wounded, including four of Khan's bodyguards.

A Taliban spokesman, Zabiullah Mujahid, claimed responsibility and said the target was Khan.

The Taliban assassination campaign is a strong sign of deteriorating security in the country, where a record number of U.S. and NATO troops have also died this year. The Obama administration is now debating whether to send more American troops to Afghanistan as its government faces allegations of widespread fraud from the disputed Aug. 20 presidential election.

U.S. Defense Secretary Robert Gates issued a stern warning to critics of a continued troop presence in Afghanistan on Sunday, saying the Islamic extremist Taliban and al-Qaida would perceive an early pullout as a victory similar to the Soviet Union's humiliating withdrawal in 1989 after a 10-year war.

"Taliban and al-Qaida, as far as they're concerned, defeated one superpower. For them to be seen to defeat a second, I think, would have catastrophic consequences in terms of energizing the extremist movement, al-Qaida recruitment, operations, fundraising, and so on," Gates said in an interview broadcast Sunday on CNN's "State of the Union."

But many Americans are skeptical of sending more troops to support a government in the midst of recounting votes from a tainted presidential election. Karzai currently has about 54 percent of the vote. If enough questionable ballots get thrown out he could drop below the 50 percent threshold needed to avoid a runoff.

Karzai's main challenger, Abdullah Abdullah, said Sunday he was satisfied so far with the recount, which is using a sampling of votes to speed the process and meet a narrowing timeframe to hold a possible runoff before winter snows block much of the country.

Two U.S. service members died Saturday in the country's south — one from a roadside bomb explosion and the other from an insurgent attack, the NATO-led force said Sunday. A British soldier died Sunday from a bomb explosion while patrolling in southern Afghanistan, Britain's Defense Ministry said.

Elsewhere, three French soldiers died in a violent storm in northeastern Afghanistan late Saturday. One soldier was struck by lightning, while two were swept away by a rain-swollen river during an operation in Kapisa province, said military spokesman Christophe Prazuck.

This year has been the deadliest of the eight-year war for U.S. and NATO troops. The six latest deaths bring to 64 the number of NATO troops killed this month.