A roadside bomb hit an American Humvee in southeastern Afghanistan (search), killing two U.S. soldiers and their Afghan interpreter, the American military said Sunday.

Another U.S. soldier was reported injured in the blast on Saturday in Ghazni province, part of the rising cost of American operations supposed to prevent militants from disrupting historic Afghan elections.

The wounded soldier was in stable condition at the U.S. base the southern city of Kandahar (search), a brief military statement said. The dead would not be identified until next of kin were informed, it said.

It was not immediately clear who carried out the bombing about 140 miles southwest of the capital, Kabul (search). But the area lies in a broad belt near Pakistan where suspected Taliban-led rebels regularly clash with U.S. and Afghan troops.

The deaths bring to about 58 the number of American soldiers killed in action in Afghanistan since U.S. forces entered the country in 2001 to drive the Taliban from power and attack its al-Qaida allies.

With accidents and deaths elsewhere, including several planes crashes, more than 130 American soldiers have died since Operating Enduring Freedom was launched in response to the Sept. 11 attacks in the United States.

Twenty-three of the combat deaths in Afghanistan have occurred this year, making 2004 the deadliest year yet and undermining assertions by American and Afghan officials that militants are on the defensive and security is improving.

Violence has intensified in recent months as the country prepares for its first post-Taliban election -- a vote for president on Oct. 9 which U.S.-backed President Hamid Karzai is widely expected to win.

U.S. Marines led offensives which killed more than 100 suspected militants during May and June in the Taliban strongholds of Uruzgan and Zabul provinces, but have failed to halt insurgent attacks.

In the past week alone, gunmen ambushed and killed a convoy carrying election workers in Uruzgan, killing two; two Afghans working for a German relief agency died in a hail of gunfire in Paktia; and twin attacks on American convoys in Zabul left six soldiers wounded, two of them seriously.

The U.S.-led force of some 18,000 last month began a new operation focused on preventing attacks on the election process. About 30,000 newly trained Afghan national police and army soldiers and up to 10,000 NATO troops are also expected to be on duty during the voting.

American commanders say increased fighting is partly due to their stepped-up operations in Taliban strongholds populated mainly by ethnic Pashtuns, from whom the Taliban draw their main support.

U.S. forces have established a string of new bases across the south and east and are spending millions on relief projects in the hope of winning over local tribes and gaining intelligence.

American officials insist the attention devoted to the election has not diluted its efforts to track down militant leaders including Al Qaeda chief Osama bin Laden, who some believe could be hiding along the mountainous Afghan-Pakistan border.