A powerful explosion heard in Baghdad's heavily fortified Green Zone as the country's polls kicked off on Thursday, police said.

Few minutes after the country's landmark election begun, a powerful explosion struck the Green Zone in central Baghdad as smoke rose over the area and sirens wailed, a police source told Xinhua on condition of anonymity.

There were no immediate reports of any casualties or damage.

The heavily fortified Green Zone, houses the Iraqi government offices and the US embassy, frequently attacked by insurgents with mortar rounds and rockets.

The blast in the heart of the Iraqi capital came just minutes after the parliamentary elections kicked off at 7:00 AM (04:00 GMT) as eligible voters headed to polling stations to elect the country's first full-term parliament since the US-led invasion toppled the Saddam Hussein regime in 2003.

Security for the vote is extremely tight to try to minimize the threat of insurgent attacks, it was reported.

(Xinhua News Agency December 15, 2005)