The explosions came during a night of shooting as fighting continued following the storming of Gaddafi's Bab al-Azizya compound by rebel fighters on Tuesday.
The leader of a rebel group told an AFP correspondent that pro-Gaddafi fighters were hidden on the road to Tripoli airport. On the run and his whereabouts unknown, a defiant Gaddafi delivered two messages during the night.
In a speech carried by the website of a television station headed by his son Seif al-Islam, he said he had abandoned his Tripoli compound in a "tactical withdrawal" after it had been wrecked by NATO warplanes.
"Bab al-Azizya was nothing but a heap of rubble after it was the target of 64 NATO missiles and we withdrew from it for tactical reasons," he said.
The speech gave no indication of where he had gone.
In a later audio message on Syrian-based Arrai Oruba television station, Gaddafi urged residents to "cleanse Tripoli of rats." He also said he had taken to the streets of Tripoli without being recognised.
"I walked incognito, without anyone seeing me, and I saw youths ready to defend their city," the strongman said, without specifying when he did his walkabout.