Shelling by the Islamic State (IS) militants on two oil terminals in Libya has started fires that have spread to giant storage tanks, officials say, according to the BBC.

The fires are reported to be raging in Sidra and Ras Lanouf, on the coast between Sirte and Benghazi.

Officials said at least 10 guards had been killed since IS attacked the neighboring ports on Monday, January 4.

Warplanes from Libya's internationally recognized government have provided air support to help defend the area.

IS has been operating in Libya for about a year, and in December France warned that the group was aiming to seize the country's oil wells.

Ali al-Hassi, of the Petrol Facilities Guard militia, said on Wednesday that neither Sidra nor Ras Lanouf had fallen to IS so far.

Firefighters, he said, were trying to control blazes at four oil storage tanks in Sidra and one in Ras Lanouf - each thought to contain more than 400,000 barrels of oil, BBC says.

Hassi also said guards had recovered the bodies of 30 militants and had captured military vehicles.

On Monday, IS said it had taken control of the town of Bin Jawad, 30km west of Sidra on the road from its stronghold in Sirte.