KABUL, Afghanistan (CNN) -- Nine U.S. troops were killed Sunday in an attack on a base in a remote province of eastern Afghanistan, a Western official said.

It was the deadliest attack on U.S. troops in Afghanistan in three years.

NATO confirmed that nine of its International Security Assistance Force troops were killed, but it didn't release the troops' nationalities. Fifteen other ISAF troops and four Afghan troops were wounded, NATO said.

"The fighting began in early morning hours and continued into the day as insurgents were repulsed from an Afghan National Army and ISAF combat outpost," said a NATO statement.

The statement continued, "Although no final assessment has been made, it is believed insurgents suffered heavy casualties during several hours of fighting."

Though details of the attack were sparse, an earlier statement from ISAF said Afghan and ISAF soldiers were involved in "heavy fighting" with insurgents at a command outpost in Kunar province.

"Insurgents have been firing at the [command outpost] with small arms, machine guns, rocket-propelled grenades and mortars, using homes, shops and the mosque in the village of Wanat for cover," according to the statement.

ISAF and Afghan soldiers, backed by air support, responded with small arms, machine guns, mortars and artillery, the statement said.

Since the start of coalition operations in Afghanistan, 470 U.S. troops have died. This figure includes Sunday's casualties.

News of the dead U.S. troops came after a suicide bomber riding a motorcycle killed at least 21 people, including four police officers, in southern Afghanistan Sunday.

The latest incidents are part of a deadly wave of weekend attacks that also included a suicide attack at an army camp in Helmand province and the death of two coalition soldiers.

http://www.cnn.com/2008/WORLD/asiapcf/07/13/afghan.bomber/index.html