CAIRO, Aug 8 (Reuters) - The chairman of Libya's National Oil Corp (NOC) on Saturday warned against the risk of a disaster at the country's oil ports due to a growing military presence with storage tanks held at capacity for months due to a blockade.

"Oil ports are closed, exporting is halted. So if these over-stocked tanks were attacked or exposed to fire or high temperature, it will lead to a massive disaster," the chairman, Mustafa Sanalla, said in a video message.

Eastern forces in the civil war have been stopping energy exports since January, bringing most output to a halt and causing storage tanks to fill.

After the latest bout of warfare in June, the NOC said mercenaries had moved into oil fields and ports held by the eastern forces.

The company, which is based in Tripoli in western Libya, seat of the internationally recognised Government of National Accord (GNA), has previously said the shutdown has caused major technical problems at the fields and ports.

Sanalla, whose video message was published on the NOC website, compared the risk of a disaster to Tuesday's blast in Beirut, where Lebanon's government said a fire ignited 2,750 tonnes of ammonium nitrate left unsecured at the port for years, killing scores of people and wounding thousands. (Reporting By Samar Hassan in Cairo; editing by Angus McDowall and Jonathan Oatis)