An explosion tore through a crowded mosque in western Afghanistan on Friday, killing at least 18 people. including a prominent cleric close to the Taliban, Taliban officials and a local medic said. At least 21 people were hurt.

The explosion in the city of Herat left the courtyard of the Guzargah Mosque littered with bodies, the ground stained with blood, video from the scene showed. Men shouted, “God is great,” in shock and horror.

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The bomb went off during Friday noon prayers, when mosques are full of worshippers.

Among the dead was Mujib-ul Rahman Ansari, a prominent cleric who was known across Afghanistan for his criticism of the country’s Western-backed governments over the past two decades. Ansari was seen as close to the Taliban, who seized control over Afghanistan a year ago as foreign forces withdrew.

His death was confirmed by the chief Taliban spokesman, Zabihullah Mujahid. Just before the bombing, Ansari had been meeting in another part of the city with the Taliban government’s deputy prime minister, Mullah Abdul Ghani Baradar, who was on a visit to Herat. He had rushed from the meeting to the mosque to get to the noon prayers, an aide to Baradar said in a tweet mourning the cleric.

Ambulances transported 18 bodies and 21 people wounded from the blast to hospitals in Herat, said Mohammad Daud Mohammadi, an official at the Herat ambulance center,

There was no immediate claim of responsibility for Friday’s blast.

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Last month, a bombing at a mosque in the capital Kabul targeted and killed a pro-Taliban cleric in an attack claimed by the Islamic State group. IS has waged a bloody campaign of attacks on Taliban targets and minority groups, particularly Shiites whom the extremist Sunni IS considers heretics. It has frequently hit mosques with suicide attacks during Friday prayers.

Herat’s Guzargah Mosque, where Ansari has long been the preacher, draws followers of Sunni Islam, the dominant stream in Afghanistan that is also followed by the Taliban.

Ansari was for years a thorn in the side of Afghanistan’s pro-Western government. In his sermons at the Guzargah, he urged his many supporters to carry out protests against the governments and preached against women’s rights.