Tripoli, July 7 (IANS) Unidentified militants in Libya's largest city of Benghazi

shot down a police helicopter Friday, killing one person in the incident, Xinhua reported early Saturday.

The police helicopter, carrying elections material, was downed by militants allegedly supporting autonomy in eastern Libya, said sources, adding that the victim's identity could not be immediately confirmed.

The killed person was a member of the committee and the pilot on board survived, reported Libya's Press Solidarity quoting a High Electoral Committee official.

The incident came a day ahead of Libyans casting their ballots for a national congress.

The elections are expected to replace the ruling National Transitional Council to supervise the government and oversee the drawing up of a new constitution following the overthrowing of Muammar Gaddafi, a ruler for four decades.

The polls are being boycotted by Libya's self-proclaimed autonomous eastern region.