The attack happened at the gate of Zabul province Provincial Council, located close to other several government buildings.
"At around 10:00 AM today, a truck loaded with over a ton of explosives was detonated at the gate of [Zabul province] Provincial Council, wounding 73 people including 16 women," Zabul province security chief Ghulam Jilani Farahi told DW.
Farahi added that four people among the wounded were in critical condition and were being taken to neighboring Kandahar province to receive medical care.
"No one has been confirmed dead so far. I don't know if the four people we sent to Kandahar died on their way. But at the moment I cannot confirm anything," Farahi said.
The Afghan official blamed the responsibility of the attack on Taliban militants who have been fighting a bloody war against Afghan government and its foreign allies since 2001.
According to news agency reports the Taliban has claimed responsibility for the attack on southern Zabul Province. The group has stepped up attacks against the Afghan government after launching its traditional summer offensive.
Another blast in Kabul killed four and wounded many others last Tuesday. Most of the victims in Taliban attacks are civilians.
NATO ended its military mission in Afghanistan in 2014 and handed over all security responsibilities to Afghan forces. The recent surge in militant attacks across Afghanistan has once again raised concerns over Afghan troop's abilities to protect their country against Taliban attacks.