Attackers have detonated explosives before storming the offices of the Save the Children charity in the eastern Afghan city of Jalalabad.
At least two people have been killed and 12 injured, officials say. It is believed about 50 staff were in the building at the time.
At least three gunmen are involved in the attack, reports say, with fighting continuing on the upper floor.
No group has yet said it was behind the attack.
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