The explosion outside the Afghan defence ministry in Kabul has caused multiple casualties, Afghan officials have said.
A police spokesman said an apparent suicide attacker on a bicycle hit the main entrance to the building around 9:00am local time.
US defence officials have confirmed defence secretary Chuck Hagel, who is visiting the country, was in a safe location and unharmed.
He had been in a meeting at a coalition facility in the city at the time of the blast.
More top news
For the second year running, Sandbanks has been identified as Britain's most expensive seaside location.
It will be drier and brighter in the south, with temperatures remaining high.
The well-respected foreign policy hawk enjoyed his greatest successes as national security adviser to President Jimmy Carter.