LAHORE, Pakistan — A bomb blast inside a mosque in southwestern Pakistan, believed to be frequented by senior Taliban figures, killed at least 15 people on Friday and wounded at least 18 more, according to police officials.

Several of the wounded were in critical condition, and hospital authorities feared the death toll could climb further.

The blast tore through a mosque during evening prayers in Quetta, the provincial capital of Baluchistan Province, which borders Afghanistan and Iran.

The Islamic State claimed responsibility for the bombing, according to the SITE intelligence group.

A local leader of a religious political party in Pakistan, who is familiar with Taliban networks in the country and spoke on condition of anonymity because of fear for his safety, said that the mosque was sometimes used by a Taliban leader, Mawlawi Abdul Hakeem, but he was not present at the time of the attack.