The blast follows a string of suicide attacks and comes days after a top rebel commander claimed that more than 200 insurgents were willing to kill themselves in assaults on U.S. forces and their allies.
Militants also used a roadside bomb to wound two U.S. troops driving in a desert in southern Helmand province Thursday, a military statement said. A purported Taliban spokesman, Qari Mohammed Yousaf, claimed responsibility.
The attack came a day after a U.S. soldier was killed and two others wounded in another roadside bombing in mountains in eastern Afghanistan.
This year has been the deadliest in Afghanistan since U.S.-led forces ousted the Taliban in 2001 for harboring Osama bin Laden. The fighting has killed more than 1,500 people as militants belonging to the Taliban, al Qaeda and other groups have stepped up attacks.
The explosion that killed the two suspected suicide bombers took place at a market place in Waish, 75 miles east of the Taliban stronghold of Kandahar, said Abdul Hakim Hungar, deputy police chief of Kandahar province. No one else was hurt.
Hungar said the militants were suspected of planning to attack government forces, and the owner of the shop they were in at the time of the blast was arrested. He said the two appeared to be Afghans.
Taliban rebels are active along the Afghan-Pakistan border, staging attacks against the Afghan government and U.S.-led coalition forces.
The guerrilla leader in the area, Mullah Dadullah, claimed in an interview with The Associated Press over the weekend that more than 200 militants "have registered themselves for suicide attacks."
He said such assaults would continue until "Americans and all of their Muslim and non-Muslim allies are pulled out of the country."
Afghanistan's government dismissed the claim as propaganda, though President Hamid Karzai said last month that he expects attacks to continue.
Unlike in Iraq, suicide attacks had been relatively rare until September, fueling fears that rebels could be adopting tactics used in the Middle East. There have been about a dozen in the past few months, including twin assaults in the capital of Kabul on Nov. 14 that targeted NATO-led peacekeepers and killed a German soldier and eight Afghans.
On Wednesday, a court in Pakistan's southwestern Quetta city sentenced Dadullah to life in prison in absentia for attempting to kill a Pakistani hard-line cleric and lawmaker in July 2004.
Dadullah, who is believed to be hiding in Afghanistan, had been charged with trying to assassinate Maulana Mohammed Khan Shirani with a roadside bomb, said Kamran Murtaza, the lawyer for Shirani. Shirani, his three aides and his driver escaped unhurt.