The Taliban claimed responsibility for the attack in Muhammad Agha district of Logar province which took place at around 8:00am (0330 GMT) Friday. [break]
The blast could be heard for several kilometres (miles), an AFP reporter in the area said.
Logar´s health director, Mohammad Zarif Nayebkhail, told AFP that up to 70 people were taken to hospital with injuries from shrapnel or flying glass.
"Up to 70 wounded have been taken to the main hospital in the district -- seven of them are (Afghan) security guards of NATO, the rest are civilians," he said. "Several of the wounded were in a serious condition."
Logar´s deputy police chief Mohammad Abed described the blast as "huge."
"The suicide attacker wanted to ram his explosive-laden vehicle into the coalition forces base but he was stopped at the gate and detonated the truck outside the base," he said.
He put the provisional toll of those injured at five -- three police and two NDS (Afghan intelligence) personnel -- adding that some houses had been destroyed by the blast.
A spokesman for NATO´s US-led International Security Assistance Force (ISAF) confirmed a car bombing in the district but said they were still "gathering information".
He could not confirm that ISAF was the target or the number of casualties.
In September, 77 US troops were wounded in a truck bombing which targeted a NATO base in Wardak province, which neighbours Logar.
US officials blamed the attack on the Haqqani network, an Afghan Taliban faction whose leaders are based in Pakistan´s northwestern tribal belt.
Civilians are increasingly caught up in the Afghan war.
The United Nations says that civilian deaths in the first half of this year rose by 15 percent to 1,462, with insurgents responsible for 80 percent.
There are currently 140,000 international troops in Afghanistan fighting a decade-long, Taliban-led insurgency alongside Afghan government forces.
Foreign combat troops are due to leave by the end of 2014 but a substantial presence is expected to remain to train Afghan security forces.
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