A suicide bomber has killed at least 30 people inside a Shia mosque in the Afghan capital Kabul, officials say.
An eyewitness told the BBC the scene at the Imam Zaman mosque, in the west of the city, "looks like a frontline".
The attacker is reported to have opened fire as worshippers gathered for Friday prayers, before detonating a bomb.
No group has so far said it had carried out the attack, but so-called Islamic State (IS) has targeted Shia mosques across Afghanistan.
A spokesman for the Afghan interior ministry said investigators were working at the scene to determine the "nature of the explosion," AFP news agency reports.
Friday's attack comes just days after police in Kabul said they had arrested a would-be suicide truck bomber, averting a major incident.
In August, more than 20 people were killed in a bomb attack against worshippers in Kabul.
A truck bomb in the Afghan capital in May killed more than 150 people.
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