KABUL, Afghanistan — Four U.S. soldiers died when their vehicle struck a land mine in central Afghanistan on, the military said.

It was unclear whether the mine was freshly laid or a leftover from the country's long wars.

The soldiers were among a group of American and Afghan officials examining a potential site for a shooting range in Logar Province, 25 miles south of Kabul, when one of their three vehicles hit the mine, spokeswoman Lt. Cindy Moore said.

She said the military is looking into the possibility the mine was old and had shifted or the vehicle had strayed from known safe routes. No one else was reported hurt.

According to Defense Department statistics, 122 American soldiers have now died since American forces invaded to oust the former Taliban government for harboring al-Qaida militants after the Sept. 11, 2001, attacks in the United States.

Many have been killed in accidents, including by mines left behind by Soviet troops who occupied Afghanistan in the 1980s or the Afghan factions who fought each other after they withdrew.

A U.S. military policeman died March 15 when his vehicle hit what appeared to be an old mine in western Afghanistan.

The worst incident was an explosion at an arms dump in southeastern Ghazni province which killed eight American soldiers in January last year.

The 17,000 American troops still in Afghanistan also face a stubborn Taliban-led insurgency.

The U.S. military says its air and ground operations along the Pakistani border killed 12 people in the past week.

Eight were suspected militants while four were civilians, including three children.