At least 12 people were killed and 15 more were wounded in an explosion inside a mosque in Shakar Dara district north of Kabul Friday afternoon, shattering cease-fire calm.

The blast happened at Haji Bakhshi Mosque in Qala-e-Murad Bek area in Shakardara district of Kabul during Friday prayer as worshippers gathered for the second day of the Eid al-Fitr holiday the Kabul police said in its statement.

TOLO News reports that sources said the bomb was placed inside the mosque.

Police said that Mufti Numan, the imam of the mosque, was also killed in the blast. 

There was no immediate claim of responsibility for the attack. Taliban militants have called a three-day ceasefire for the holiday, which marks the end of the Ramadan holy fasting month.

The blast came a day after at least nine people were killed in two blasts in Kunduz and Kandahar provinces and less than a week after an explosion at a school killed 80 people, most of them schoolgirls from the ethnic Hazara Shi'ite Muslim minority.  The Taliban denounced that attack and no one has claimed responsibility for it.  U.S. officials believe it may have been the work of a rival militant group such as Islamic State (IS).