Two senior Bangladeshi opposition leaders have been executed for war crimes committed during the 1971 independence war with Pakistan after their last-ditch pleas for clemency were rejected.

The justice minister, Anisul Huq, said Ali Ahsan Mohammad Mujahid and Salahuddin Quader Chowdhury had been hanged at Dhaka’s central jail in a move that was celebrated by supporters of the ruling Awami League.

“Both of them have been hanged. The execution took place at 00.45am [18.45 GMT on Saturday],” Huq said.

Hundreds of police had been stationed outside the jail in Dhaka’s old quarter where scaffolds had been prepared to execute the pair.

The first sign that the executions had taken place came when four ambulances were driven away from the prison shortly before 1am.

The 67-year-old Mujahid was sentenced to death for war crimes including the killing of the country’s top intellectuals. He is the second most senior member of Bangladesh’s largest Islamist party, Jamaat-e-Islami.

Chowdhury, 66, was convicted for atrocities including genocide during the 1971 war when the then East Pakistan split from Islamabad. He sat in the legislature six times and was an aide to Khaleda Zia, leader of the main opposition Bangladesh Nationalist Party.

Bangladesh’s supreme court dismissed the two men’s final appeals on Wednesday, upholding the death sentences passed by a controversial domestic war crimes tribunal in 2013.

The pair were among more than a dozen leaders of the opposition alliance convicted by a tribunal set up by the secular government in 2010.

The convictions triggered Bangladesh’s deadliest violence since independence, with about 500 people killed, mainly in clashes between Jamaat-e-Islami activists and police.