A Bangladeshi Islamist party allied to the opposition has elected a new chief untainted by war crime allegations, seeking to turn the page after the execution of several of its top leaders.

Jamaat-e-Islami said in a statement late Monday it had sworn in former school teacher Maqbul Ahmed as its leader after a secret ballot of party members.

Ahmed takes over from Motiur Rahman Nizami, who was hanged in May after a controversial tribunal convicted him of murder during the country's 1971 war of independence with Pakistan.

Four other top leaders, including the party's secretary general, its two joint secretaries and its main financier, have been executed since 2013 following trials that rights groups have condemned as unfair.

They were tried by the same war crimes tribunal set up by the secular government of Prime Minister Sheikh Hasina, which said Jamaat leaders had to be prosecuted to heal the wounds of the war.

Sources close to Jamaat said Ahmed, believed to be in his early seventies, had been chosen from a panel of three senior party officials who had not been tainted by war crimes.

In his debut speech he paid tribute to Hasina's father, who led the war of independence against Pakistan, in a sign the party is looking to break from its past policies.

‘He is an experienced leader and a very good organiser,’ said Abul Asad, the editor of the pro-Jamaat Bengali daily Sangram.

‘He has said he wants to forget the pains and sorrows of the past and wants to look forward.’

Jamaat, Bangladesh's largest Islamist party, was barred from contesting the 2014 general election, effectively disenfranchising millions of its supporters.

The main opposition Bangladesh Nationalist Party -- allied to Jamaat -- subsequently boycotted the polls, which became a one-horse race held against a backdrop of violent protests.

Many observers believe the lack of genuine democracy in the country has contributed to a recent upsurge in Islamist violence, including a deadly siege at an upmarket Dhaka cafe in July.

Jamaat opposed Bangladesh's independence from Pakistan, but denies its leaders were involved in genocide, murders and rapes during the nine-month long conflict.

The conviction and execution of Jamaat officials plunged Bangladesh into one of its worst crises in 2013, when tens of thousands of Islamist activists clashed with police in protests that left some 500 people dead.

In the same year the government launched a nationwide crackdown on Jamaat activists in which tens of thousands of Islamists were either detained or charged over the protests.