The Foreign Office on Friday evening said it had summoned an Indian diplomat to protest over the acquittal of the alleged mastermind behind the deadly Samjhota bombings in 2007, reported Waqt News.
Foreign Office spokesperson Nafees Zakaria said in a statement that SSarkar had confessed to his involvement in the 2007 Samjhota bombings that killed at least 48 Pakistanis.
"Pakistan expects that India takes proper actions in this regard and bring to justice the culprits of deadly terrorist attack of Samjhota Express ," added the statement.
Naba Kumar Sarkar, the alleged ringleader behind the attack, was among seven Hindu radicals acquitted after prosecutors failed to prove their guilt.
Sarkar, better known by his nickname Swami Aseemanand, remains in prison pending trial over his role in two separate bomb attacks ─ one on a mosque and another on the Samjhota Express that together killed nearly 75 people.
A confession by Sarkar led investigators to a group accused of staging a series of blasts targeting Muslims. He later retracted his confession but police were able sweep up suspected radicals, including a serving Indian army office and former members of Rashtriya Swayamsevak Sangh.
The prominent right-wing Hindu group bears considerable influence in India, and is the ideological fountainhead of Indian Prime Minister Narendra Modi's ruling nationalist Bharatiya Janata Party.