KABUL, Sept. 11 (Xinhua) -- A powerful explosion occured near U.S. embassy in Kabul, capital of Afghanistan, early Wednesday morning, according to multiple sources.

Images circulated on social media showed a plume of smoke rising near the building of U.S. embassy in the exclusion zone of Kabul, where several other embassies are also located.

The blast was caused by a rocket attack, a local reporter Jawad Jalali said.

Alarm was sounded by U.S. embassy after the explosion and can be heard in surrounding areas.

There is no official report of casualty yet, but casualties are feared. No government officials can be reached for more details. No one has claimed responsibility for the blast.

September 11 marks the 18th anniversary of the attack by Al-Qaeda on World Trade Center in New York in 2001. The United States invaded Afghanistan in late 2001 in response to the attack.

The negotiations between the United States and Taliban to end the 18-year-long Afghan war has recently been called off by U.S. president Donald Trump.