The leader of Bangladesh's top Islamist party Jamaat-e-Islami is set to hang within days after the Supreme Court on Thursday upheld his death sentence for war crimes.

Motiur Rahman Nizami was convicted of murder, rape and orchestrating the killing of intellectuals during the country's 1971 war of independence.

He was tried by a controversial war crimes tribunal set up by the government that has sparked deadly protests, with Jamaat and its ally the opposition Bangladesh Nationalist Party (BNP) saying it is aimed at eliminating their leaders.

Attorney General Mahbubey Alam said jail authorities would begin preparing for Nizami's execution once they received a copy of the verdict.

‘We're satisfied. Now there is no bar to execute him unless he seeks clemency from the president and the president pardons him,’ he told AFP after the Supreme Court dismissed the 73-year-old's final appeal.

Security has been stepped up in Dhaka, already tense after a string of killings of secular and liberal activists and religious minorities by suspected Islamist militants.

In the last two weeks alone, two gay rights activists, a liberal professor and a Hindu tailor who made derogatory comments against the Prophet Mohammed have been hacked to death.

Hundreds of people who had campaigned for the Islamist leaders to be tried for their roles in the 1971 war burst into impromptu celebrations at a square in central Dhaka and in the port city of Chittagong.

‘Justice has finally prevailed. We hope the government will now execute him without wasting any time,’ said Imran Sarker, a secular blogger.

Three senior Jamaat officials and a key BNP leader have been executed since December 2013 for war crimes despite global criticism of their trials.

Jamaat said the charges against Nizami, a former government minister, were false and aimed at eliminating the leadership of the party.

- Bodies dumped -

Nizami took over as party leader in 2000 and played a key role in the victory of an Islamist-allied government in the 2001 general election.

The 1971 conflict, one of the bloodiest in world history, led to the creation of an independent Bangladesh from what was then East Pakistan.

Prosecutors said Nizami was responsible for setting up the Al-Badr pro-Pakistani militia, which killed top writers, doctors and journalists in the most gruesome chapter of the war.

Their bodies were found blindfolded with their hands tied and dumped in a marsh on the outskirts of the capital.

The trial heard Nizami ordered the killings, designed to ‘intellectually cripple’ the fledgling nation.

He was convicted in October 2014 by the International Crimes Tribunal, which was established in 2010 by Prime Minister Sheikh Hasina's government and has sentenced more than a dozen opposition leaders for war crimes.

Rights groups say the trials fall short of global standards and lack international oversight, while the government says they are needed to heal the wounds of the conflict.

‘It will be for future generations to decide whether this (war crimes) law was passed to serve a special purpose,’ lead defence lawyer Khandaker Mahbub Hossain told reporters after the court's verdict on Thursday.

Amnesty International called for an immediate halt to Nizami's execution, citing concerns over the fairness of the trials carried out by the tribunal.

‘Victims of past atrocities deserve better than a flawed process,’ said Jameen Kaur, the group's campaigns director for South Asia.

In 2013 the convictions of Jamaat officials triggered the country's deadliest violence in decades.

Around 500 people were killed, mainly in clashes between Islamists and police, and thousands of Islamists were arrested.

Jamaat has called a nationwide strike for Sunday to protest against the court's decision, although analysts said violence was unlikely given the extent to which the party's support base has been weakened.