Islamic State claimed responsibility for the bombing, which it said targeted an Afghan Taliban seminary
The death toll from the bombing of a mosque in the southwestern Pakistani city of Quetta rose to 15 on Saturday, officials said, in an escalation of militant violence.
An improvised explosive device ripped through the mosque during Friday evening prayers, killing 13 people and wounding more than 20, police said.
Islamic State claimed responsibility for the bombing, which it said targeted an Afghan Taliban seminary.
Mineral and gas-rich Balochistan, of which Quetta is the capital, is at the centre of the $60 billion China-Pakistan Economic Corridor, part of China's Belt and Road project.
But violence in the province has fuelled concerns about the security of projects such as a planned energy link from western China to Pakistan's southern port of Gwadar.
Friday's attack was the second in the city this week, while police said they had foiled another by killing a suicide attacker Rawalpindi city near Islamabad after he shot and killed two policemen.
"Two of the wounded people died overnight in the hospital," said provincial home minister Zia Langove, adding that six people were still in a critical condition.
The Taliban denied in a statement that some of its members, including a top commander, were killed.
Local officials in Quetta's police and district administration would not confirm whether the Dar-ul-Aloom Shariah seminary belonged to the Afghan Taliban under a state policy which denies the presence of the group on its soil.
However, two officials said on condition of anonymity that the seminary was part of the Afghan Taliban.
Baluchistan has long been the scene of an insurgency by separatist and nationalist groups, who want a greater share in revenues earned from the local resources.
Islamist militants, including Islamic State which consists of splinters from local Taliban and sectarian groups, also have a strong presence in the region.