Shahidullah Shadid, a spokesman for the Wardak provincial governor, said one suicide bomber detonated a vest rigged with explosives outside a compound housing the district governor's office as well as local police and Afghan army headquarters. A second bomber driving a fuel tanker detonated his bomb on a road separating the compound from the base.
Shadid said the dead included eight civilians and four Afghan police.
Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack, which he said was targeting the U.S. base.
Government officials said the first attacker blew himself up to try to eliminate the Afghan security force guarding the compound and clear the way for the truck to hit the base down the road from the governor's complex. The second bomber then blew up the fuel tanker as he was approaching the base. One of the town's main bazaars is also located near the bomb site.
"A small explosion happened followed by a big one caused by a truck," said eyewitness Hamidullah, who like many Afghans goes by one name. "In these explosions a lot of people were wounded and also a large number of shops were destroyed. I fell down on the ground and everything around me was destroyed."
Officials said the second blast was far larger than the first.
"It was a very powerful explosion. It broke windows all over the area," said provincial police chief Gen. Abdul Qayum Bakizai. "Most of the injuries are from broken glass from the windows of homes and shops. It was so powerful we couldn't find much of the truck."
The governor's office said in a statement that 59 people were wounded 2 NATO troops, 47 civilians and ten Afghan police officers.
Last year, the same base in Wardak was the target of another suicide bombing. That blast, which occurred on the anniversary of the Sept. 11 terrorist attacks against the United States, wounded 77 American soldiers and killed five Afghans. No U.S. troops were killed when the massive truck bomb exploded outside the base.
In a separate incident Saturday, NATO said that two U.S. soldiers were killed in eastern Ghazni province. It did not provide any further information or details about the deaths, the first this month. A total of 53 foreign troops were killed in Afghanistan in August.
The United States and other countries have already begun drawing down their forces in Afghanistan as part of a strategy that aims to hand over security responsibility to the Afghans by the end of 2014, when nearly all foreign troops are set to leave the country. President Barack Obama has pledged to remove 23,000 U.S. troops by the end of September, bringing the number of American forces down to 68,000.
There are currently 129,000 troops serving with the coalition, according to US Maj. Gen. Joseph Reynes Jr., director of operations at the Allied Joint Forces Command in Brunssum, the Netherlands. He said earlier this week that the number will drop to 108,000 by the end of October and dip under 100,000 by the end of the year.
The troops are to be replaced by Afghan army and police units, but many have questioned the effectiveness of an Afghan force that has high desertion rates and is often poorly disciplined. The Afghan security forces are supposed to reach a high of about 350,000 at the end of the year.