DEVELOPING STORY – Large explosion in Kabul near several ex-patriate offices, including Americans. American casualties being reported.

A big explosion rocked the center of the Afghan capital on Sunday, but there was no immediate word on the cause, the extent of damage or casualties.

The explosion shook office windows in an area of Kabul close to the U.S. Embassy, the U.N. headquarters and several government buildings.

A truck loaded with wood and packed with explosives was detonated outside DynCorp’s office in the Shar-e-Naw district, home to many aid agencies and foreign firms. DynCorp provides Afghan President Hamid Karzai’s bodyguards and trains the fledgling police force.

Karzai’s office said that seven people were confirmed dead — two Americans, three Nepalese and two Afghan nationals, including a child. However independent witnesses at the scene said the death toll was likely to rise.

At least 28 people were wounded in the blast, including at least four Americans. The attack was the worst in Kabul since December 28 last year and the second major bomb attack in the country in as many days.