Rauf had been named in a dossier of evidence in that attack given to Pakistan by India
Pakistan has detained dozens of alleged militants after a suicide attack in Indian-held Kashmir last month which sent tensions between the nuclear-armed foes soaring, its interior minister said Tuesday.
Among those detained in Islamabad's latest crackdown on banned groups was Abdul Rauf - who a security source told AFP is a younger brother of Masood Azhar - the leader of Pakistan-based militant group Jaish-e-Mohammad (JeM) that claimed responsibility for the February 14 attack.
Rauf had been named in a dossier of evidence in that attack given to Pakistan by India, the interior ministry said.
"We have launched a crackdown against proscribed organisations and have taken 44 individuals into custody, including Mufti Abdul Rauf and Hammad Azhar," state minister for the interior Shehryar Afridi told reporters in Islamabad.
He did not give any further names, clarify what groups those detained allegedly belonged to, or say if they would face charges.
The February 14 attack killed 40 Indian paramilitaries and spurred tit-for-tat air raids between India and Pakistan across the highly militarised Line of Control, the de facto border in the disputed Himalayan region of Kashmir.
Both sides claimed they had shot each other's warplanes down, igniting fears of an all-out conflict as world powers pleaded for restraint.
Pakistan captured one Indian pilot, releasing him on Friday in a bid to pull both countries back from the brink, though tensions remain high.
Rauf is a little-known younger brother of Masood Azhar, the security source said. He added that "Hammad Azhar" was an alias, but did not say who for.
Indian officials were sceptical of the detentions Tuesday. "We have seen Pakistan make arrests before, and then the people are released," an Indian government source told AFP.
India, along with the US, has pressured Pakistan to take action against militancy.
"If they still do not mend their ways, We have told them what will happen," Prime Minister Narendra Modi told an election rally in central India Tuesday.
Afridi said Pakistan was "not taking this action under pressure from anyone". Islamabad has vehemently denied involvement in militant attacks, and said there are no safe havens left for terror groups on its territory.
JeM leader Masood Azhar remains in Pakistan, foreign minister Shah Mehmood Qureshi told CNN last week, adding that he was "very unwell" and could not leave his house.