ISLAMABAD: Pakistan is "deeply saddened" over Bangladesh's execution of wealthy tycoon and top Jamaat-e-Islami financier Mir Quasem Ali for "alleged crimes committed before December 1971 through a flawed judicial process", Foreign Office (FO) Spokesman Nafees Zakaria said on Sunday.

Bangladesh hanged Ali on Saturday for alleged war crimes. The key Jamaat-e-Islami leader was convicted in November 2014 of a series of crimes committed during the 1971 independence conflict, including the abduction and murder of a young fighter.

"The act of suppressing the Opposition through flawed trials is completely against the spirit of democracy," Zakaria said.

Ali is the last prominent JI leader to face execution. Five opposition leaders including four JI leaders have been executed for war crimes since 2013.

"Ever since the beginning of the trials, several international organisations, human rights groups, and international legal figures have raised objections to the court proceedings, especially regarding fairness and transparency, as well as harassment of lawyers and witnesses representing the accused," he said.

"The government of Bangladesh should uphold its commitment, as per the Tripartite Agreement of 1974, wherein it 'decided not to proceed with the trials as an act of clemency'," Zakaria said, adding that "recriminations for political gains are counter-productive".

"Pakistan believes that matters should be addressed with a forward-looking approach in the noble spirit of reconciliation," he said, adding that Pakistan offers its deepest condolences to the bereaved family members.

Mir Quasem Ali was said to be a key commander of the Al-Badr militia in the southern port city of Chittagong during the 1971 war, and later became a shipping and real estate tycoon.

His son Mir Ahmed Bin Quasem, who was part of his legal defence team, was allegedly abducted by security forces earlier in August, which critics say was an attempt to sow fear and prevent protests against the imminent execution.

The Jamaat-e-Islami, which is banned from contesting elections has labelled the charges against Ali “false” and accusing the government of exacting “political vengeance”.

Past convictions and executions of high-profile JI leaders have triggered violence in Bangladesh, which is polarised along political lines.