KABUL (BNO NEWS) -- A roadside bomb killed a U.S. Navy SEAL in southern Afghanistan on Saturday, the U.S. Department of Defense and the NATO-led International Security Assistance Force (ISAF) confirmed on Sunday.

The U.S. Department of Defense said 26-year-old Petty Officer 1st Class Caleb A. Nelson of Omaha, Nebraska was killed when his vehicle struck an improvised explosive device (IED) while conducting a combat patrol in Zabul province, located in the country's south.

Nelson was a United States Navy SEAL assigned to an East Coast-based Naval Special Warfare unit based in Norfolk, Virginia. Other details about Nelson or the patrol he was on were not immediately released.

Also on Sunday, the U.S. Department of Defense confirmed 32-year-old First Sergeant Billy J. Siercks of Velda Village, Missouri died on Wednesday as a result of wounds suffered a day earlier in Logar province when insurgent attacked his unit using indirect fire. Siercks died at a hospital in Landstuhl, Germany.

Coalition casualties in Afghanistan have been rising sharply in recent years with a total coalition death toll of 709 in 2010, making it the deadliest year for international troops since the war began in response to the September 11, 2001 terrorist attacks on the United States.

There are currently more than 130,000 ISAF troops in Afghanistan, including some 90,000 U.S. troops and more than 9,500 British soldiers. U.S. President Barack Obama previously ordered a drawdown of 10,000 American troops later this year, with another 23,000 U.S. troops to return home next year.

So far this year, at least 468 coalition service members have been killed in Afghanistan. Most troops are American and are killed in the country's south, which is plagued by IED attacks on troops and civilians. The deadliest incident happened in August when a U.S. helicopter crashed in eastern Afghanistan, killing 30 U.S. troops, seven Afghan troops and an Afghan interpreter.

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