Plumes of smoke rose on Wednesday morning, local time, over Kabul, and in a call with an embassy employee, he confirmed the explosion, but did not have details, according to Al Arabiya.
This is the first major attack recorded in the Afghan capital since President Donald Trump announced the cancellation of US-Taliban talks, while on the verge of an agreement to end the longest US war.
Two car bombs rocked Kabul last week, killing several civilians and two NATO members.
Trump cited the death of a US soldier in one of those blasts as a reason to describe talks between the United States and the Taliban as "dead."
Trump said on Monday that talks with the Taliban, which seemed to lead to a historic deal after 18 years of war in Afghanistan, were "completely over."
"For me, it's over," he told reporters as he left the White House for North Carolina over a weekend peace plan, after he canceled on Sunday secret Camp David talks with Taliban leaders over Thursday's deadly attack in Kabul where one American soldier and 11 others were killed.
With regard to the withdrawal of some 14,000 US troops from Afghanistan, he said: "We would like to withdraw, but we will go out on time."
Trump stressed that Washington has intensified strikes against its enemies unprecedentedly in Afghanistan since ten years, after he announced the suspension of negotiations with Taliban.