No U.S. troops were killed in the attack and none of the injuries appeared to be life threatening.
The massive bomb loaded on a truck filled with firewood struck the gate of a combat post in Wardak province.
Officials said the Afghans killed included a policeman and four civilians, including a 3-year-old girl. Another 17 Afghans - 14 civilians and three policemen - were wounded. The provincial governor said the blast was so powerful it damaged about 100 nearby shops.
The Taliban claimed responsibility for the attack. Earlier, they had issued a statement vowing to fight until all foreign troops leave.
The radical Islamic movement, which gave shelter to Osama bin Laden and al-Qaida when it ruled Afghanistan, also stressed that it had no role in the Sept. 11 attacks, and it accused the U.S. of using them as a pretext to invade the country.
"The Afghans have an endless stamina for a long war," the statement said. "Through a countrywide uprising, the Afghans will send the Americans to the dustbin of history like they sent other empires of the past."
The Associated Press contributed to this story.
