This week, as we remember the nearly 3,000 American citizens who died in the rubble of the World Trade Center and the Pentagon or in a remote field in Pennsylvania on Sept. 11, 2001, we also should think about the civilians who are still dying in Afghanistan.

Consider, for instance, the recent American airstrikes on Azizabad, a village in western Afghanistan, on Aug. 22. The United Nations, Afghan government officials and independent witnesses all say that the United States killed about 90 civilians in these strikes, most of them women and children. Cellphone videos of the scene show motionless children lying under checkered shawls and veiled women shrieking alongside them.

According to a report by Carlotta Gall of the New York Times, dozens of freshly dug graves are scattered in the village's cemeteries, some so small they could fit only children. The U.S. initially said that many fewer civilians had died, but it has now promised a thorough investigation.

It's a grisly story but hardly an isolated one. The month before the Azizabad incident, Afghan officials say that American airstrikes near Kabul killed 27 civilians at a wedding party -- including the bride. In another incident, on March 4, 2007, nine civilians died when their mud home north of Kabul was hit by two 2,000-pound bombs dropped by U.S. aircraft. American officials said they were aiming for two insurgents seen entering the house after firing a rocket at a U.S. military outpost, according to Human Rights Watch.

Not surprisingly, civilian casualties infuriate Afghans. This was brought home clearly in May 2006 after an American military convoy on a road north of Kabul lost control and plowed into a group of Afghans, killing five. In the days that followed, mobs of Afghans attacked businesses and hotels owned by foreigners; at least 14 died and more than 90 were injured.

Areport last September from the United Nations concluded that Western airstrikes were among the chief inspirations for suicide attackers within the country and that they engendered resentment against both the Afghan government and Western forces. The number of suicide attacks in Afghanistan went up six times from 2005 to 2006, to 136, and Taliban insurgents carried out more than 140 suicide bombings in Afghanistan in 2007.

Civilian casualties also seem to be a key factor in the marked erosion of support by Afghans for the American presence in their country. In 2005, 68% of Afghans rated U.S. efforts in Afghanistan positively, but that number dropped abruptly to 57% in 2006 and to 42% in 2007.

The casualty numbers remain high even seven years into the war. According to a Human Rights Watch report released this week, in 2006, 230 civilians died as a result of U.S. or NATO attacks, 116 of them during airstrikes. In 2007, at least 321 Afghan civilians were killed by Western airstrikes. So far in 2008, at least 119 have been killed by U.S. or NATO airstrikes.

The 2008 estimate does not include the airstrike near Azizabad because the U.S. military has maintained that only five to seven Afghan civilians were killed in that incident. Cellphone videos of the carnage don't conclusively prove this wrong, but they do raise enough questions that Gen. David D. McKiernan, the senior NATO commander in Afghanistan, has ordered a high-level investigation.

Aware of how politically sensitive the issue is, Afghan President Hamid Karzai has been calling for years for Western forces to show greater restraint in carrying out airstrikes in civilian areas. Indeed, shortly after the Azizabad strikes, he ordered a review of whether U.S. and NATO forces should be allowed to use airstrikes in or around villages.

Why are U.S. and NATO forces causing so many civilian casualties? One explanation may be that there are too few Western boots on the ground. Afghanistan, which is 1 1/2 times the size of Iraq and has a larger population, only has about 70,000 American and NATO soldiers stationed there. In Iraq, by contrast, there are about 145,000 American troops on the ground. This translates to heavier Western reliance on airstrikes in Afghanistan and the inevitably higher cost in civilian casualties those produce.

According to the U.S. Air Force's Central Combined Air and Space Operations Center, between January and August there were almost 2,400 airstrikes in Afghanistan -- three times as many as in Iraq.

Another factor is the Taliban's execrable tactic of using civilians as human shields. Because the Taliban operates in and around settled residential areas, it is inevitable that operations by the U.S. against the group will involve civilian casualties.

Civilians in Afghanistan have been caught in the crossfire for too long. Over-reliance on airstrikes is counterproductive in the battle for Afghan hearts and minds. President Bush's announcement this week that he will send nearly 5,000 additional troops to Afghanistan is a good way to start ameliorating this situation, but it is not enough.

The overall rules of engagement in Afghanistan need to change, as was promised by NATO Secretary-General Jaap de Hoop Scheffer, who said in July that the alliance would start using smaller bombs in Afghanistan in an attempt to decrease civilian casualties.

Limits on the size of bombs dropped were indeed imposed, but civilian casualties have continued at a level that is unacceptable. In a welcome development, McKiernan announced this week that NATO troops will focus more on house searches led by Afghan forces, with the permission of the homeowner sought first, and he also has reminded his top commanders of the importance of proportionality and restraint.

Hopefully, more coalition boots on the ground and revised rules of engagement will lessen the continued Western reliance on bombing from the air. After all, American civilians are not the only innocents to have suffered the results of the horrific Sept. 11 terrorist attacks.