The employee told people who called the embassy to try again Tuesday with any questions, the Iranian news agency IRNA reported.
IRNA said it confirmed Saad Mojbar, the Libyan ambassador to Tehran, had left the city "under pretext of taking a leave."
Meanwhile, U.S. President Barack Obama said Monday Moammar Gadhafi's regime is near its end.
"The situation is still very fluid," Obama said. "There remains a degree of uncertainty, and there are still regime elements who pose a threat. But this much is clear: The Gadhafi regime is coming to an end and the future of Libya is in the hands of its people."