The blasts were heard yesterday but their location was unclear. Earlier, the embattled strongman said his regime would not fall.
"NATO is wrong if it thinks it can topple the regime of this country," Gaddafi told thousands of supporters in Sabha, some 750 kilometres (450 miles) south of Tripoli, in an audio message.
"Our only choice is resistance: we are on home ground and are not afraid of your war machine," he told supporters in his clan's desert stronghold, addressing NATO directly.