The EU urged Libyan politicians to back a unity government, as the Islamic State group claimed suicide bombings that killed dozens and sparked fears of a jihadist expansion on Europe's doorstep.
The deal aims to bring together rival administrations that split the country in August 2014 -- when an Islamist-backed militia alliance overran Tripoli, forcing the internationally-recognised government to take refuge in the east -- and tame chaos that has plagued Libya since 2011.
The EU's push is the latest in longstanding diplomatic efforts to bring together the country's warring factions, with European Union foreign affairs chief Federica Mogherini also pledging to give Libya 100 million euros ($108 million) to battle IS.
The funds would be available from the first day the unity government comes to power because the security situation "needs to be tackled immediately", she said.
Mogherini made the remarks in Tunis, where she separately met with Fayez al-Sarraj, a businessman named in a UN-brokered national unity government as prime minister designate, as well as other Libyan lawmakers.
Her remarks came as IS claimed responsibility for a truck bomb attack on a police training school which left more than 50 people dead, according to a security source, as well as buildings charred and cars turned into twisted wrecks.
It was the deadliest single attack in Libya since the 2011 revolution that toppled longtime dictator Moamer Kadhafi.
- 'Very worrisome' -
IS, which launched an offensive against Libya's oil heartland this week, also said it was behind Thursday's suicide bomb attack on a checkpoint in Ras Lanouf, home to a key oil terminal on the country's northern coast.
The Red Crescent said six people, including a baby, died in that attack.
Fears the jihadists are establishing a new stronghold on Europe's doorstep have added urgency to efforts to bring together warring factions in a country beset by chaos since 2011.
In December, after months of negotiations, a minority of lawmakers from both sides signed on to the UN-brokered national unity deal which has yet to win the full support of the two legislatures.
The heads of Libya's parliaments have warned the UN-brokered deal has no legitimacy and that the politicians signing the agreement represented only themselves.
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Analysts say these divisions are bolstering the position of IS.
"The situation has become very worrisome... with IS taking advantage of the chaos, the collapse of the central authorities and wars by proxy," said Karim Bitar, head of research at the French Institute of International Relations.
The international community has been pleading for months with Libya's rival parliaments to embrace the UN-brokered deal.
Mogherini said she had "fruitful and concrete" talks with Libyan politicians on how the EU can help the future government in the "fight against terrorism and namely against Daesh (IS)".
"The best response to terrorism especially to Daesh will be a Libyan response" and a government to unite Libyans, she said, adding that the EU could help provide "training and advising".
- 'Reducing the trust deficit' -
UN Secretary General Ban Ki-moon condemned Thursday's attacks and also urged unity among Libyans, while the UN Security Council called on the country's rival groups to speed up the formation of a unity government.
Bitar said the establishment of a national unity government was a matter of "urgency" but he warned international efforts could fail due to "numerous suspicions" on the ground.
Mohamed Eljarh, a non-resident fellow with the Atlantic Council's Hariri Centre, agreed.
He said the latest attacks claimed by IS "would not end the feud in Libya, but could at best result in reducing the trust deficit between the various armed and political groups as they attempt to cooperate and help each other in the face of IS's expansion".
The chaos in Libya since 2011 has led to its rise as a stepping stone for migrants crossing the Mediterranean to Europe.
The IS offensive against the oil terminals in Ras Lanouf and nearby Al-Sidra in Libya's so-called "oil crescent" have, meanwhile, come as the jihadist group has tried for weeks to push east from its stronghold in Sirte.
Officials have warned the already crumbling state could be paralysed if IS, which is reported to have at least 3,000 fighters in Libya, seizes control of oil resources.