Libyan medics say a helicopter crashed near the eastern city where the internationally-recognized parliament is based, killing all six people on board, including the military adviser of a powerful general.

Tobruk Medical Center says in a statement Tuesday that the son of the adviser to Gen. Khalifa Hifter was also on board the helicopter, which crashed the night before.

The Libyan news portal al-Wasat quoted Col. Al-Safi al-Sanini as saying that the MI8 helicopter was on an official mission to Ras Lanuf oil terminal, once of three such facilities captured by Hifter's forces last week.

The debris was found 120 kilometers (75 miles) west of Tobruk, where the parliament is based. Hifter is allied with the parliament, which has rejected a U.N.-backed government based in the capital, Tripoli.