Zidan has been struggling with militias since he was named a year ago by parliament to lead the first democratically formed government since Gadhafi's ouster and death. The tensions were enflamed by last Saturday's raid by U.S. special forces that snatched a Libyan al-Qaida suspect off the streets of the capital and whisked him off to custody in a U.S. warship.
The raid angered many militiamen, who accused Zidan of collaborating in the abduction of a Libyan citizen. Zidan, who has cultivated close security cooperation with the U.S., denied any prior knowledge of the operation. The raid is believed to have prompted Zidan's own abduction on Thursday, when gunmen stormed into the luxury Tripoli hotel where he lives and took him away, holding him for several hours.
Islamic hard-liners held marches in Tripoli on Friday, denouncing the raid and criticizing the government.
The militias originated in the "revolutionary" brigades that fought Gadhafi's forces. Since his ouster, they have refused to disarm and have mushroomed in size and power. Many have been enlisted by the state to serve as security forces, since the army and police are weak, underequipped and under-paid. But they often continue to act as armed vigilante factions with their own interests, and some follow radical al-Qaida-style ideologies or are believed to have links to the terror organization.
Touting themselves as "revolutionaries," some have long demanded Zidan's removal since he once served as an ambassador under Gadhafi. Militias have in the past besieged government buildings and carried out kidnappings including the abduction last month of the defense minister's son, apparently to pressure him against trying to rein in the groups.
Zidan appeared on TV alongside members of his government, and warned that "there are those who want to take Libya into the unknown. They want to turn Libya into Afghanistan or Somalia."
"They claim that I do not love the revolutionaries," he said, countering that he had veterans of the anti-Gadhafi fight in his Cabinet. "But there are those who have come with guns and bombs to press various individual demands, and I have refused them. They impede the development of the army and police."
"We want a nation of institutions, with an army and police," he said. "But there are those who want to terrorize the state and the courts and the institutions, and this we refuse."
Zidan said his captors told him they belonged to the Revolutionaries Operation Room, a security agency that was recently created out of several militias, including Islamic hard-liners. Nouri Abu Sahmein, the head of the parliament, formed the agency as a parallel security force for the capital.
Zidan said his kidnappers told him they were acting on orders of their leaders. However, Abu Sahmein, who visited him while he was in custody, was not involved, he said, thanking him for his help in ensuring his freedom. A similar militia grouping, called the Anti-Crime Department, is also believed to have been involved.
The abduction raised alarm among some Libyans over the boldness of the militias. The Revolutionaries Operation Room includes many militiamen who refused to join the military.
In a statement on its website, the group accused Zidan's government of collaborating in the U.S. operation that captured al-Qaida suspect Nazih Abdul-Hamed al-Ruqai, known by his alias Abu Anas al-Libi. Al-Libi is accused by the U.S. in connection with the 1998 bombings of its embassies in Tanzania and Kenya.
In was not immediately clear if Friday's car bombing in Benghazi was connected to Islamic militant anger over al-Libi's capture.
The blast went off in the morning outside a building housing the consulates of Sweden and Finland, some of the last diplomatic missions operating in the city. It shattered windows and blew out doors, but none of the eight or nine staffers inside were injured, according to their countries' governments.
Violence is particularly sharp in Benghazi, which has seen a string of attacks on diplomatic facilities, most notably the Sept. 11, 2012 storming of a U.S. diplomatic post that killed the U.S. ambassador and three other Americans. That attack has been blamed on militants believed to be linked to al-Qaida.
In January, militants opened fire on the car of the Italian consul in Benghazi. He was not hurt in the attack. In June 2012, the British ambassador's vehicle was attacked with rocket-propelled grenades, injuring two of his bodyguards, as he visited the city.
Last week, a mob descended on the Russian Embassy in the capital, Tripoli, climbing over its walls, pulling down a gate and firing in the air, prompting Moscow to evacuate its diplomats and their families. The attack was sparked when a Russian woman was arrested for allegedly killing a Libyan air force officer and his mother.