NATO said it lost radar contact with a drone helicopter conducting a reconnaissance flight over Libya on Tuesday, denying one of its attack helicopters had crashed.

The alliance's command centre in Naples, Italy, lost track of the unmanned autonomous helicopter drone at 0720 GMT, NATO military spokesman Mike Bracken said in a statement.

"This drone helicopter was performing intelligence surveillance and reconnaissance over Libya to monitor pro-Kadhafi forces threatening the civilian population," he said.

The military alliance was looking into the reason behind the incident.

"NATO confirms it has not lost any attack helicopters during Operation Unified Protector and will provide more information on the incident as it becomes available," Bracken added.

Libyan state television on Tuesday showed footage of a burnt-out helicopter it identified as an Apache, reportedly downed near Zliten, 160 kilometres (100 miles) east of the capital.

The caption on the television, which quoted military sources, read: "Images of the Apache helicopter shot down by the people's army."

It was not immediately possible to verify if the helicopter was an Apache.

Zliten is 40 kilometres west of the rebel-held port city of Misrata.

NATO has been using combat helicopters over Libya in an attempt to break the stalemate in the conflict.