The explosion happened in front of a shopping mall and bank. At least one burned-out U.N. car could be seen at the scene.
The U.N. refrained from releasing details, but said some of the casualties were from its team working on a mission in eastern Libya.
Libyan National Army (LNA) spokesman Ahmed Mismari told reporters two of those killed were guards with the U.N. Libya mission (UNSMIL). He added that 10 people had been wounded, including children.
The attack came as the U.N. is brokering a truce in the capital Tripoli, where the eastern-based LNA, under Khalifa Haftar, has been trying to incite a revolt in the capital amid signs of popular agitation against the Tripoli-based National Accord Government (GNA), headed by Prime Minister Fayez Al-Serraj, backed by the U.N. This is part of the chaos in Libya that has taken place since Muammar Gaddafi was toppled in 2011 with the strong support of European and U.S. forces.
On Friday, the government in Tripoli said it had already accepted a U.N. proposal for a ceasefire during the holiday.
Around the time of the blast, Haftar announced a halt to military operations for 48 hours during the Muslim Eid al-Adha holiday, which started on Saturday, according to a statement from his forces in Benghazi.
U.N. Secretary-General Antonio Guterres on Saturday condemned the bombing, a spokesman said in a statement.
“The U.N. does not intend to evacuate from Libya,” the assistant secretary-general for peace operations, Bintou Keita, later told the Security Council, which also condemned the attack.