KABUL, Afghanistan - A roadside bomb in eastern Afghanistan killed a U.S. service member, and suspected Taliban rebels gunned down an Afghan woman accused of spying for the coalition, officials said today.

The spate of violence deepens concerns over security in the east and south of the country ahead of key legislative elections set for Sept. 19, Afghanistan's next major step toward democracy after two decades of war and civil strife.

The U.S. military said a roadside bomb exploded Tuesday near a vehicle in eastern Ghazni province where an American unit was conducting operations to "disrupt enemy activity in the region."

Two American troops were evacuated to the main U.S. base at Bagram, north of Kabul, where one of them died of his wounds shortly after arrival - the fifth American soldier killed in a week. The second was in stable condition.

More than 17,000 U.S. troops are in Afghanistan, and more than 170 have died in and around the country since Operation Enduring Freedom began in late 2001 to oust the hardline Taliban regime after the Sept. 11 attacks on the United States.

Three-and-a-half years on, Taliban-led insurgents remain active. Fighting with coalition forces has intensified this year. More than 900 people have died in violence since March and officials warn it could escalate before the polls as insurgents step up sabotage efforts.

On Monday, one U.S. service member and at least 16 suspected Taliban rebels were killed in fighting in the volatile southern province of Zabul. Coalition aircraft joined the battle, sparked when a U.S. and Afghan patrol came under fire from militants using small-arms and rocket-propelled grenades.

Last Thursday, two U.S. troops drowned when their Humvee vehicle slid into a river near Jalalabad city. A third was killed the same day by a roadside bomb in Paktika province, near the Pakistan border.

Afghan officials, meanwhile, reported that six militants shot and killed an unidentified woman in Zabul province's Mizan district after bursting into her house late Tuesday.

District chief Haji Mohammed Yaunas said the militants accused the woman of giving information to American forces.