At least 31 persons were injured in the attack which began at 2.50 p.m. when a suicide bomber blew himself up near a gate of the bank, opening the way for another three who entered the bank and began a shootout with security forces, Xinhua news agency reported.
Four militants and two police officers were among the dead, according to reports.
"We have received eight bodies and 31 injured persons in the hospital in Gardez city," Shir Mohammad, head of the public health department in Gardez city, said.
The office of Afghan President Ashraf Ghani took to Twitter to condemn the attack, saying: "Pres @ashrafghani condemns attack on Kabul Bank in Gardez as a cynical assault on Afghan people living their lives and doing business."
No group has claimed responsibility for the deadly attack. This is the second high profile attack in the eastern region of Afghanistan over the past four days.
The previous attack for which the Islamic State (IS) group claimed responsibility saw armed militants storm the state-run television station in Jalalabad city earlier this week. Six people were killed in the attack.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)