Friday's blast tore through a mosque in Mastung in the southern province of Balochistan after a bomber detonated his explosives near a police vehicle where people were gathering for a procession to mark the birthday of the Prophet Mohammad.
Pakistani officials have long claimed that India sponsors violent groups in Pakistan - claims India has always denied.
"Civil, military and all other institutions will jointly strike against the elements involved in the Mastung suicide bombing," interior minister Sarfaraz Bugti told media in Balochistan's capital, Quetta.
"RAW is involved in the suicide attack," he added, referring to India's Research & Analysis Wing (RAW) intelligence agency. He did not provide details or evidence on the alleged involvement.
India's foreign ministry and a government spokesperson did not immediately respond to requests for comment.
Wasim Baig, the spokesman for Balochistan's health department, said seven more people had died in hospital since Friday, which had caused the rise in the death toll, adding that more patients remained in critical condition.
A second attack on Friday at a mosque in northern Khyber Pakhtunkhwa had killed at least five people. Police on Saturday filed a report to launch an investigation, saying they had sent DNA from the suicide bomb attacker to be analysed.
No group has claimed responsibility for either attack. A surge in militant attacks in Pakistan's western provinces has cast a shadow on election preparations and public campaigning in the run-up to January's national vote, but until now the attacks had mostly targeted security forces.
The Pakistani Taliban (TTP), responsible for some of the bloodiest attacks in Pakistan since the group's formation in 2007, denied responsibility for Friday's blasts.
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