Three ministers from Bangladesh`s last elected government, including the head of the largest Islamic party, were freed Sunday, a prison official said, just a month before the country goes to polls.

Motiur Rahman Nizami, leader of the Jamaat-e-Islami, and two other ministers from the Bangladesh Nationalist Party-led government were last week detained over a coal mining graft case.

`All three have been freed on bail just a few minutes ago,` head of Bangladesh prisons, brigadier general Zakir Hassan, told AFP.

The move came ahead of December 18 elections, with the BNP and its four-party Islamist alliance, which includes the Jamaat, already threatening to boycott the polls.

The country`s army-backed emergency government is keen to ensure the polls are credible and has released the BNP`s leader and two-time ex-premier Khaleda Zia from detention to secure her party`s participation.

But Zia and her alliance have repeatedly said they would not take part in polls unless a state of emergency is lifted fully and scores of her party workers are released from prison.

The government has detained the politicians as part of a crackdown on corruption.

Bangladesh has been ruled by a military-backed government since January last year when months of political turmoil prompted the country`s powerful army to cancel polls and impose the state of emergency.

After pushing through electoral and political reforms, the government has promised to hand over power to a civilian elected government from the first day of 2009.

The BNP-led alliance won a two-third majority when the last parliamentary elections were held in 2001.