Another eyewitness, Allah Noor, said the blast was very strong.
“I came out and had crossed the street when an explosion happened," he said. “Right after the explosion, people nervously started evacuating wounded victims to hospital."
The Italian Emergency Hospital, one of Kabul's clinics that treated the victims, said it received 14 casualties from the site, with four dead on arrival.
Khalid Zadran, a spokesman for the Kabul police chief, said worshippers were intentionally targeted as they were leaving the Wazir Akbar Khan Mosque.
“Targeting mosques and worshippers is an unforgivable crime, the nation should cooperate with the regime in eliminating criminals,” said Taliban government spokesman Zabihullah Mujahid.
The Islamic State group — a top rival of the Taliban since their takeover in Afghanistan just over a year ago — has previously targeted mosques and worshippers, and especially members of Afghanistan’s minority Shiites in attacks.
The United Nations mission in Kabul tweeted that the bombing was another “bitter reminder of ongoing insecurity and terrorist activity in Afghanistan."
“Our thoughts are with the families of those killed, wishing speedy recovery to the injured,” added the mission, known as UNAMA.
Faiez reported from Islamabad.