By Ian MacWilliam
BBC regional analyst
Suicide bombing was once unheard of in Afghanistan, but it has now become common as insurgents seek to destabilise the internationally-backed government in Kabul.
There were five times more suicide attacks in 2006 than in 2005
The latest figures show there were five times more suicide attacks in Afghanistan last year than in the previous year.
The tribal people of Afghanistan have a proud warrior tradition, and historically suicide attacks have never been a part of it.
Warriors known as ghazis might die fighting those they considered infidels, but would not set out to kill themselves.
One of the earliest suicide attacks in Afghanistan happened four years ago when a taxi packed with explosives blew up near a bus carrying German peacekeepers.
There was a sharp upsurge last year, and suicide killings have now become a common tactic used by Taleban and other insurgents opposed to Kabul's popularly elected government.
The attack at Bagram was the fourth in the past week. Suicide attacks have been most commonly used by Arab militants who oppose any Western involvement in Muslim countries.
A Taleban spokesman claimed the Bagram attack was carried out by an Afghan but reports suggest that many, if not most, suicide attackers in Afghanistan are foreign militants.
They have imported the tactic, particularly from Iraq, to pursue what they see as their jihad in Afghanistan, despite the support of most Afghans for the international forces trying to bring peace there.