The Interior Ministry spokesman, Zemeri Bashary, said 12 people were killed, including two policemen, and that 42 were injured. Dr. Salam Jalali, a Public Health Ministry official, said 54 had been injured. He said the wounded had been taken to six different hospitals in Kabul, complicating officials' efforts to keep track of the casualties.

The explosion occurred a little before 8 a.m., as ministry employees were reporting to work, near a narrow dirt road where employees and civilians pass through a security gate.

Bashary said the suicide attacker had been acting suspiciously, then tried to get close to a big gathering of people just beyond a police checkpoint.

"The police warned him to stop, and then he detonated himself," Bashary said.

A witness said he saw the bomber run from police, who had tried to search him.