A tribunal has jailed the former chief of Bangladesh's largest Islamist party while he awaits trial on war crimes charges.

89-year-old Ghulam Azam is accused of collaborating with Pakistan's army in carrying out murders and rapes during Bangladesh's war of independence from Pakistan. He was head of the opposition Jamaat-e-Islami party.

On Wednesday, the government's International Crimes Tribunal in Dhaka rejected Azam's bail and ordered him jailed.

Five other top Islamist leaders have been arrested since the special war crimes tribunal was created last year.

Azam's lawyer criticized the tribunal's denial of bail, citing his client's age and health problems.

Bangladesh, formerly known as East Pakistan, won independence in 1971 after a nine-month war with Pakistan. Three million people were killed and hundreds of thousands of women were raped. Rights groups have also alleged “ethnic cleansing” that targeted East Pakistan's Hindu minority.

Jamaat-e-Islami and its ally, the country's main opposition Bangladesh Nationalist Party, have said the ruling Awami League party set up the special war crimes tribunal in order to target political opponents.

New York-based Human Rights Watch has said legal procedures used by the tribunal fall short of international standards.