A Libyan official says at least 60 people have been killed after a truck bomb hit a police training school in Libya.

The bomb was placed in a lorry and exploded in the western city of Zliten as hundreds of police recruits were gathering, mayor Miftah Lahmadi said.

UN envoy to Libya Martin Kobler said on Twitter that the blast was a suicide attack:

I condemn in the strongest terms today's deadly suicide attack in Zliten, call on all Libyans to urgently unite in fight against terrorism

— Martin Kobler (@KoblerSRSG) January 7, 2016

Dozens have been injured.

Oil attack

The blast follows Monday's attack by Islamic State on the Al-Sidra oil complex which lies about 400 kilometres (248 miles) west of Benghazi.

Firefighters struggled to put out the flames as an oil tank was set alight in clashes between IS and Libya's government troops.

It took several hours before the Islamist fighters were pushed back.

A spokesmen for the government forces said six of its troops had been killed in the attack, as well as five IS militants.

A spokesman from the Harouge Oil Company on Wednesday that the whole area was in danger with firefighters trying to control blazes at four oil storage tanks in Sidra and one in Ras Lanouf.

Each tank is believed to hold more than 400,000 barrels of oil.

Officials at Sirt Oil Company appealed for help in dealing with the fire.

IS offensive

IS has been trying to take control on the oil fields which are east of its coastal stronghold of Sirte - they failed to take control of Sidra in an attack last October.

Libya has been in political chaos since former dictator Colonel Muammar Gaddafi was deposed and killed in 2011 with IS gaining increasing influence in the area.

It has been run by rival administrations since 2014 when an Islamist-backed militia alliance took over Tripoli, forcing the government to set up a base in the east.

The UN is urging both sides to begin implementing a power-sharing deal agreed in December.