Updated

Suspected Islamic militants fired a rocket into a field next to the U.S. Embassy here Thursday, Afghan authorities said. The blast occurred less than two hours after Defense Secretary Donald H. Rumsfeld (search) left the Afghan capital.

There were no reports of injuries in the 6:15 p.m. explosion about 300 yards from the embassy compound, and 100 yards from the headquarters of international peacekeepers in Kabul.

Rumsfeld had earlier held talks with President Hamid Karzai (search) at his palace elsewhere in the city. The defense secretary left about 4 p.m. to continue his tour of Central Asia.

"We are reviewing our security posture," a spokesman at the heavily fortified embassy said. He spoke on condition of anonymity and declined further comment.

The blast underlined the violence plaguing Afghanistan two years after a U.S.-led offensive swept the Taliban (search) regime from power and heightened tension in Kabul ahead of a loya jirga (search), or grand council, next week to ratify a constitution.

Thursday's blast echoed around the city, drawing swarms of Afghan police and soldiers to an expanse of newly tilled field next to the U.S. Embassy compound.

Security officials walked the field with flashlights. One emerged from the darkness holding a piece of shrapnel he said was from a small rocket. Reporters were evicted before the impact site could be found.

Troops from the 5,700-strong International Security Assistance Force blocked roads around the U.S. compound.

Lt. Cmdr. Frank Coburn, a British ISAF spokesman, said a forensics team was sent to the site. He said he couldn't confirm witness accounts suggesting it was a rocket.

Matyullah Ramani, a senior Kabul police officer, said: "It was Taliban or (Gulbuddin) Hekmatyar" — a renegade commander allied with the Taliban. "They are trying to disrupt the loya jirga."

Karzai's administration has little control outside the capital because of attacks by pro-Taliban insurgents and fighting among provincial warlords.

Recently, attacks on aid workers and Afghan government staff have increased sharply in the south and the east, forcing relief agencies to reduce their work there.

Kabul has also been affected.

Five rockets rained down on the city on the anniversary of the Sept. 11 attacks, slightly injuring one Canadian civilian working at a peacekeepers' base.

On Nov. 22, an explosion in the garden of an upscale hotel in Kabul frequented by foreigners shattered windows, but caused no injuries.