Suicide bombers in Libya attacked a police training school and a checkpoint Thursday, killing more than 56 people and prompting renewed calls for unity in a country torn by rivalries and jihadist threats.
The deadliest incident was in the coastal city of Zliten, where a truck bomb exploded outside the school, killing more than 50 people, a security source said.
The attack was the deadliest since the 2011 revolution that toppled longtime dictator Moamer Kadhafi.
A witness in Zliten, about 170 kilometres (100 miles) east of Tripoli, told AFP some 300 men, mainly coast guards, were inside the compound at the time.
Health ministry spokesman Ammar Mohammed Ammar said 50 to 55 people were killed and at least 100 wounded. Victims were rushed to several hospitals and urgent calls were issued for blood donations.
The blast blew out windows and charred concrete buildings inside the compound and turned cars into black and twisted wrecks, reported an AFP correspondent from the scene.
Hours later another bomber drove an explosives-packed car into a checkpoint in a key oil region under recent assault by the Islamic State (IS) group, killing six people, including a baby.
"I am at the morgue where six bodies from the site of the attack were brought, including the body of a child," said Mansour Ati, the head of Libya's Red Crescent. Eight people were also wounded.
Ossama al-Hodeiri, a spokesman for the security forces that guard nearby oil facilities, told AFP: "A driver in a Toyota Land Cruiser blew himself up at a checkpoint at the entrance to the town of Ras Lanouf."
Hodeiri, who was at the scene, aid three guards and a 16-month-baby were among the dead.
There was no immediate claim of responsibility for the attacks in Zliten or Ras Lanouf but IS has claimed previous suicide bombings and other atrocities.
IS has been growing in power in Libya, feeding on the chaos that has gripped the country since the revolution.
On Monday it launched an offensive against the oil terminals in Ras Lanouf and nearby Al-Sidra, after trying for weeks to push east from its stronghold of Sirte.
The terminals are located in the so-called "oil crescent" along the northern coast, and officials have warned of crippling consequences if the jihadists manage to seize control of Libya's oil resources.
- Calls for unity -
Libya has had rival administrations since August 2014, when an Islamist-backed militia alliance overran Tripoli, forcing the government to take refuge in the east.
The internationally recognised government condemned the attack as a "cowardly terrorist act" and called for the lifting of an arms embargo it says has prevented authorities from tackling IS.
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A deputy defence minister for the Tripoli-based government, Mohammad Bashir al-Naas, vowed to revenge.
"The perpetrator is not known but he is a coward. He kills our sons from the shadows. We must avenge them and do everything possible to protect them," he told a press conference.
Hundreds of people braved the cold and high winds Thursday afternoon to attend a prayer service for the victims of the truck bombing at Zliten's stadium.
The United Nations is pressing Libya's rival sides to implement a power-sharing deal agreed last month on forming a unity government.
UN envoy to Libya Martin Kobler said implementing the political agreement was crucial.
"I condemn in the strongest terms today's deadly suicide attack in Zliten, call on all Libyans to urgently unite in fight against terrorism," he wrote on Twitter.
EU policy chief Federica Mogherini also urged Libyans to back the unity deal.
"The people of Libya deserve peace and security and... they have a great opportunity to set aside their divisions and work together, united, against the terrorist threat facing their country," she said.
Italy, the former colonial power in Libya, offered its support in helping to bring stability.
"In the face of this terrorist threat, the first answer must be unity among Libyans," Foreign Minister Paolo Gentiloni said. "It is urgent that the recently signed political agreement be implemented."
- 'Struggle for power' -
World powers fear Libya could descend further into chaos and become an IS stronghold on Europe's doorstep.
In a report to the UN Security Council in November, International Criminal Court chief prosecutor Fatou Bensouda said that IS had been responsible for at least 27 car and suicide bombings in Libya in 2015.
The group claimed responsibility for suicide car bombings in the eastern town of Al-Qoba in February that killed at least 40 people.
Calls have been growing for a possible foreign military intervention to bring stability to Libya and contain IS, which is reported to have at least 3,000 fighters in the country.
Mohamed Eljarh, a Libya analyst with the Atlantic Council, said the Zliten attack was aimed as a show of strength and to highlight the vulnerability of security forces.
"Despite IS's evident presence in Libya, various political groups are still consumed with their struggle for power and control."