Footage from the private television station showed several supporters of the opposition taking down the Libyan flag and smashing a bust of Qaddafi to pieces in the embassy's yard.
The group, led by consul Ibrahim Al-Furis, took over the mission's seal and the safe and declared they are now joining the opposition.
Qaddafi is clinging to power despite a four-month-old NATO air campaign and fighting with the opposition seeking an end to his 41-year rule.
The group detained the charge d'affaires of the embassy and his secretary, who declined to denounce the Libyan leader. The two were later allowed to leave, bTV said.
At the same time, the Bulgarian Foreign Ministry declared Ibrahim Al-Furis persona non grata and asked him to leave the country in 24 hours.
The ministry declined to give reasons for its move, citing international agreements under which diplomats can be expelled without explanation, but said it was not linked to the storming of the embassy.
"I want to say that in connection to what is happening now, our decision remains unchanged," Foreign Minister Nikolai Mladenov said. "Until we know who is who at the Libyan Embassy, we are suspending our contacts with the embassy."
An official source said Al-Furis led the attack on the embassy after he learned he was to be expelled and he is not recognized as a representative of the opposition Transitional National Council (TNC).
Last month, Bulgaria officially recognized the TNC as representatives of the Libyan people after its foreign minister visited their stronghold at the city of Benghazi.
Bulgaria has temporarily closed its mission in Tripoli and there are no Bulgarian diplomats in Libya, a Foreign Ministry spokeswoman said.
On the war front, a hospital worker in western Libya said Monday NATO forces struck a local hospital and killed seven people. Libyan government minders brought journalists to the destroyed hospital in the town of Zlitan, about two hours drive east of the capital Tripoli. The reporters were also taken to several food warehouses that the government said were damaged in the airstrikes and were still burning.
Ambulance driver Osama Mahmoud said three doctors were among the dead at the Zlitan hospital.
Residents said NATO planes bombed the buildings early Monday morning. A NATO spokesperson in Naples said the alliance would not release information on the strikes before Tuesday.
The warring sides were nowhere near reaching a solution to the months-long conflict. The UN envoy to Libya and the Benghazi-based opposition council said they had discussed some general ideas for triggering a political process to end the war but there was no firm initiative on the table.
Abdul Elah Al-Khatib told Reuters after the meeting that he would be heading to Tripoli on Tuesday to canvas views there.
