They believe that the death of Hafiz Ahmadullah, the Taliban leader and brother of  Haibatullah Akhunzada . might have been a plot of the Pakistani establishment or its spy agency, the ISI.

"Pakistanis always wanted to use Taliban as a bargain with the US. Now with Jammu and Kashmir issue going out of hand, they don't want peace process to move forward. But, Taliban wants to move forward. So, the killing of Taliban chief is a message," says an Indian Intelligence source.

A powerful improvised explosive device (IED) blast, which occurred inside Kuchlak Madrassa, located close to Quetta city, in Pakistan on Friday left at least four people killed and 25 others injured.

Al Jazeera quoting sources said: "It is true that the brother of Akhunzada, Hafiz Ahmadullah, has been killed in the explosion."  It added that two of Haibatullah's nephews were also wounded in the blast.

The explosion was carried out with the help of a time device, which was planted under the wooden chair of the prayer leader when he started delivering the Friday sermon, police and bomb disposal squad officials were quoted as saying by Dawn News.

Sources told the newspaper around 50 people were present in the mosque when the blast ripped through its main hall. The deceased were later identified as Hafiz Hamdullah, Haji Mohammad Sarwar, Rahim Gul and Mohammad Khan.

The Deputy Inspector General of Police, Quetta, Abdul Razzaq Cheema, told Dawn News: “An explosive time device was planted under the wooden chair of the prayer leader.”

According to government sources, the brother of the AfghanTaliban leader was also killed.

The seminary was known for its ISI linkages from where the Afghan Taliban was also extended support.

Another Taliban source told the news channel, "This mosque was a place where most of the Taliban members used to meet and discuss issues."

"The duties of the mosque were handed over to Ahmadullah by Haibatullah after he was appointed as the emir of the Taliban group [in 2016]," the source said.

Haibatullah, in his late 50s and originally from Kandahar province, fought against the Russians during the 1980s and then joined the Taliban movement in 1994 under the leadership of late Taliban leader Mullah Omar, who established strict Islamic law in Afghanistan, reported the news channel.

South Asia experts say the incident is an early signal of Pakistan's failed Afghan strategy after a "failed Kashmir policy."

Security officials have started investigating the incident.

No group has claimed responsibility for the incident so far.