A suicide bomber killed at least 27 people and wounded dozens in an attack Monday at a crowded mosque in Kabul, according to reports from the Afghan capital.

The attacker reportedly blew himself or herself up inside the Baqir ul Olum mosque, used by members of the predominantly Sunni Muslim country's Shiite minority, during a ceremony

There was no immediate claim of responsibility.

Afghan Chief Executive Abdullah Abdullah denounced the attack as "a war crime and an act against Islam and humanity," saying it targeted innocent mourners, including children.

"Our security forces will hold the perpetrators accountable by bringing them to justice," he tweeted. "These terrorists and their harboring states will pay a heavy price for these atrocities against the Afghan people."