A suicide bomber killed at least 37 people in a mosque in Afghanistan's relatively peaceful north on Friday as worshippers gathered for holiday prayers, police officials said.
The attack, on the first day of the Muslim Eid al-Adha holiday, happened in Maimana, capital of Faryab province, said Lal Mohammad Ahmadzai, a spokesman for police in the Afghan north.
"The suicide bomber detonated explosives when our countrymen were congratulating each other on the Eid holiday," Ahmadzai said, adding that almost half of the dead were police.
It was not immediately clear if the Faryab police chief, who was not killed in the attack, was the target, Ahmadzai said.
"As soon as the police chief got in his vehicle the bomber detonated his explosives. It looks like the target was a large number of security forces," Ahmadzai said.
Violence is intensifying across the country, 11 years into the NATO-led war, sparking concerns over how the 350,000-strong Afghan security forces, often the target of the Taliban, will manage once most foreign troops leave by the end of 2014.