KABUL, Afghanistan — Militants killed two U.S. troops in eastern Afghanistan on the anniversary of 9/11, making 2008 the deadliest year for American forces in the country that sheltered al-Qaida while it plotted the terror attacks on New York and Washington.

The NATO-led force said one soldier was killed when insurgents attacked a compound. The separate U.S.-led coalition said a second service member died in combat. No other details were released, but a Western military official told The Associated Press that both troops were American.

Thursday's deaths brings to 113 the number of troops who have died in Afghanistan, surpassing last year's record toll of 111, according to an AP tally. Last year's count included one American killed just over the border in Pakistan.

Afghanistan was the launching pad for al-Qaida's terrorist attacks on Sept. 11, 2001. In response, U.S. forces invaded in October 2001 and drove the Taliban out of power in a matter of weeks.

At a ceremony in Kabul commemorating the Sept. 11 attacks, Col. Cody Smith said the date is a reminder of the terror experienced by those killed in the U.S. attacks experienced.

"That is what drives me, to fight for freedom all over the world because those people that died were in terror of seeing the fire, of seeing ... their lives being taken from them," Cody said. "We should fight, so that freedom reigns and terror does not."

Osama bin Laden, leader of the al-Qaida network, is believed to be in the lawless tribal belt on the Pakistan-Afghanistan border.

Once derided as a ragtag insurgency after the fall of their regime, Taliban fighters have transformed into a fighting force advanced enough to mount massive conventional attacks. Suicide and roadside bombs have turned bigger and deadlier than ever.

The number of Arab, Chechen and Uzbek militants flowing into the Afghan-Pakistan theater have increased this year, bringing with them command expertise the Taliban had lacked in previous years.

Top U.S. generals, European presidents and analysts say the blame lies to the east, in militant sanctuaries in neighboring Pakistan. As long as those areas remain havens where fighters arm, train, recruit and plot increasingly sophisticated ambushes, the Afghan war will continue to sour.

Some 33,000 U.S. troops are now stationed in the country, the highest level since 2001. Overall, more than 65,000 troops from 40 nations are deployed in Afghanistan.

U.S. troops in Afghanistan on Thursday remembered those killed in the Sept. 11 attacks during ceremonies at bases around the country. In Kabul, a top U.S. general said terrorism still remains a threat to the world.

Maj. Gen. Robert Cone told those gathered for the ceremony at Camp Eggers that terrorists have struck in London, Russia and Bali, Indonesia since the 9/11 attacks.

"These attacks are reminders that the threat of terrorism is real and still a danger to the entire world," he said.

Cone's command in Kabul trains and equips the fledgling Afghan security forces — the centerpiece of the American strategy of turning Afghanistan into a country that can defend itself and away from the days when bin Laden used it as a safe haven to launch the attacks on the United States.

Associated Press reporter Fisnik Abrashi contributed to this report.