Local officials say the incident took place in Asadabad district of Kunar province at the entrance of provincial office.
Eyewitnesses say the possible target of the suicide bomber was Haji Khanajn who was a local leader of uprising force in Dangam district.
Officials at provincial health directorate say following the incident 40 civilians have been taken to nearby hospitals.
However, it is feared the casualty toll may rise.
Some of those critically wounded have been shifted to Nangarhar Regional Hospital which has better arrangements for emergency situations compared to the medical facilities in Kunar.
No armed insurgent groups including Taliban has yet to take the responsibility of the attack.
The incident happens amid ongoing efforts for resumption of the peace talks with different insurgent groups.