Updated

Clashes erupted in Bangladesh Sunday between police and supporters of the country's biggest Islamic party ahead of a court verdict against a top Islamist for allegedly masterminding atrocities during the 1971 liberation war against Pakistan.

Some 400 Jamaat-e-Islami activists burnt a police van and hurled crude bombs in the capital Dhaka, police said, to protest what they say are false charges against Ghulam Azam, 90, who could face the death penalty if convicted by the war crimes court on Monday.

Previous sentences by the controversial court sparked the country's worst political violence since independence.

A police officer was seriously injured in the latest clashes after being hit by a rock, assistant police commissioner Saifur Rahman told AFP.

Azam was the head of the Jamaat-e-Islami party during the war in which the government says millions were killed, many by the militias he allegedly helped create to support the Pakistani army.

The International Crimes Tribunal -- set up by the secular government in 2010 -- will deliver its verdict against Azam on Monday, prosecutor Sultan Mahmud told AFP.

Prosecutors have sought the death penalty for Azam, comparing him to Nazi leader Adolf Hitler. They describe him as a "lighthouse" who guided all other war criminals and the "architect" of the militias which committed many of the 1971 atrocities.

Jamaat, the country's largest Islamic party and a key member of the opposition, has called a nationwide strike on Monday to protest the verdict, a statement posted at the party's website said.

Azam is no longer politically active but is seen as Jamaat's spiritual leader. He faces five broad charges of planning, conspiracy, incitement, complicity and murder and torture in regard to the atrocities, alleging a total of 61 crimes, Mahmud said.

Azam's lawyer Tajul Islam said the charges were based on newspaper reports of speeches Azam gave during the war, which led to the creation of Bangladesh.

"The prosecution has completely failed to prove any of the charges," he told AFP.

The verdict against Azam will be the fifth to be delivered by the tribunal. Three Islamists have been sentenced to death and one given life imprisonment.

The verdicts triggered nationwide protests by Jamaat, leading to mass violence in which 150 people were killed in clashes with police.

Eight more opposition politicians -- six from Jamaat and two from the main opposition Bangladesh Nationalist Party -- are also on trial.

The court last month also ordered an influential British Muslim and an American citizen to stand trial in absentia.

The opposition has criticised the cases as politically motivated and aimed at settling old scores rather than meting out justice.

Unlike other war crimes courts, the Bangladesh tribunal is not endorsed by the United Nations. The New York-based Human Rights Watch group has said its procedures fall short of international standards.

The government maintains the trials are needed to heal the wounds of the 1971 war in which it says three million died. Independent estimates put the death toll at between 300,000 and 500,000.