"The reports I've received from the hospital indicate that most people are in critical condition. I'm scared the death toll will rise," he said.
It was not immediately clear who was behind the explosion, which occurred next to a popular market outside the mosque, but similar acts in the past have been blamed on Taliban.
Also on Thursday, Afghan and international forces killed 13 armed men during operations in the south, while a top Taliban commander was also captured.
Ten Taliban-linked fighters were killed in the province of Ghazni along a key highway linking the capital Kabul to southern Afghanistan, the interior ministry said in a statement.
It added "these terrorists were attacking passengers and supply convoys" and said two other fighters were wounded and some others captured.
Mahboobullah Sabawoon, the chief of Gilan district where the operation took place, confirmed the incident but put the death toll at nine.
The defence ministry meanwhile said in a separate statement that three Taliban fighters were killed in an operation elsewhere in Ghazni. It gave no further details.
The interior ministry also said a prominent Taliban commander was captured in Taliban-infested southern Uruzgan province.
The commander identified as Mullah Tor Jan was deputy governor of Helmand province during the Taliban's rule, provincial police chief Juma Gul Hemat said.
"The capturing of Mullah Tor Jan is a big achievement for the police," the ministry's statement said.
More than 70,000 foreign troops, the bulk of them operating under Nato's International Security Assistance Force (Isaf), are stationed in Afghanistan.
The Taliban last month announced it would launch a new offensive in the Afghan spring, as weather conditions improve in the mountainous country - but Isaf dismissed the statement.
However, the violence has increased.