U.S. Marines and Georgian Army soldiers run to the extraction point during Operation Northern Lion II in Helmand province, Afghanistan, July 3, 2013.

A large explosion rocked Afghanistan's capital near the U.S. Embassy in the early hours of Wednesday on the anniversary of the 9/11 attack on the United States.

A plume of smoke rose over Kabul just after midnight and sirens could be heard. An embassy employee reached by phone confirmed the explosion but had no details. There was no immediate official comment.

It would be the first major attack in the Afghan capital since President Donald Trump abruptly called off U.S.-Taliban talks over the weekend, on the brink of an apparent deal to end America's longest war.

Two Taliban car bombs shook Kabul last week, killing several civilians and two members of the NATO mission. Trump has cited the death of a U.S. service member in one of those blasts as the reason why he now calls the U.S.-Taliban talks "dead."

The 9/11 anniversary is a sensitive day in Afghanistan's capital and one on which attacks have occurred. A U.S.-led invasion of Afghanistan shortly after the 2001 attack toppled the Taliban, who had harbored Osama bin Laden, the al-Qaida leader and attacks mastermind.

In the nearly 18 years of fighting since then, the number of U.S. troops in Afghanistan soared to 100,000 and dropped dramatically after bin Laden was killed in neighboring Pakistan in 2011.

Now about 14,000 U.S. troops remain and Trump has called it "ridiculous" that they are still in Afghanistan after so long and so many billions of dollars spent.

It is not clear whether the U.S.-Taliban talks will resume.