KABUL — Two roadside bombs that struck back-to-back and only miles apart hit two U.S. military vehicles in Afghanistan today, killing four American troops, U.S. and Afghan officials said.

U.S. military officials have predicted a 50 percent spike in IED attacks in Afghanistan this year as militants step up attacks and thousands of more troops pour into the country.

The deaths bring to 64 the number of U.S. forces killed in Afghanistan this year, according to an Associated Press count based on military figures. That far surpasses the 36 troops killed through the first five months of 2008, the deadliest year for American forces since the 2001 U.S.-led invasion to oust the Taliban.

Col. Greg Julian, the top U.S. spokesman in Afghanistan, said the two attacks occurred "not too far away from each other." He declined to give further details, including where the strikes took place, because family members hadn't yet been notified. He confirmed the deaths of four Americans.

By The Associated Press