Nouri Abusahmain, president of the Libyan General National Congress, said Zidan was in "good spirit" and heading to his office, CNN reported.
"He's in good shape, the prime minister, and going to his office," Abusahmain said. "He's fine, he's in good spirits."
Gunmen snatched Zidan from the Corinthia Hotel in Tripoli and put him into a convoy of waiting cars, a hotel clerk said. The luxury hotel where Zidan lives is a popular residence among government officials.
The clerk said no guns were fired during the incident and the gunmen were respectful and "caused no trouble."
Zidan's office initially called the abduction a "rumor" on its Facebook page, but later posted an update that it was "coerced by kidnappers to deny the report."
The Operations Room of Libya's Revolutionaries, the militia that took the prime minister, said it detained him because of financial and administrative corruption charges.
However, the justice ministry said there was no arrest warrant for Zidan, characterizing the act as a kidnapping, CNN said.
Euronews reported the militant group said Zidan's abduction was in response to a recent raid by special U.S. forces who captured senior al-Qaida operative Anas al-Liby in Tripoli Saturday.
Al-Liby, real name Nazih Abdul Hamed al-Ruqai, is wanted in the the 1998 bombings of U.S. embassies in Kenya and Tanzania.
Zidan publicly denied knowing about the raid beforehand and the Libyan government demanded the U.S. government explain. His assertion was undercut by U.S. officials who said the Libyan government tacitly approved the raid, triggering public ire over what was viewed as a violation of Libya's sovereignty with government consent.
Zidan's abduction has brought to light the shortcomings in the Libya's security sector, but NATO and the country's leaders haven't reached agreement on a 5-month-old request from Libya for assistance to bolster its defenses, Stars and Stripes reported.
NATO Secretary-General Anders Fogh-Rasmussen condemned the Zidan incident during a news conference at his headquarters in Brussels.
"I think it is clear to everybody that something needs to be done to ensure security in Libya," Rasmussen said.
"I can confirm that Libyan authorities have requested NATO assistance to build or reform the security sector," Rasmussen said. "We have been exploring that request for quite some time and we are still looking into it."
Stars and Stripes said it was unclear what was preventing Libya and NATO from reaching an accord.