The NATO-led Resolute Support mission said an explosion occurred just after 5.30 a.m. and that there had been casualties. It said force protection and medical teams were responding but gave no additional information, Reuters reported.
Abdul Shokor Qodosi, the district governor of Bagram, said that at least three people were killed and 13 injured in the blast, which he said occurred near a dining facility.
He said the cause of the blast was unclear.
The Taliban's spokesman, Zabihullah Mujahid, claimed responsibility for the attack in a message on his Twitter account.