Six explosions have been heard in the centre of the Libyan capital, Tripoli, near the fortified Bab al-Aziziya compound of Col Muammar Gaddafi.
Smoke could be seen rising in the area at dawn on Thursday.
The compound has been the target of a number of Nato air strikes in recent months.
The alliance imposed a no-fly zone in Libya in March as Col Gaddafi's forces threatened to overrun rebel-held parts of the country.
There was no official comment from the Libyan government on the latest explosions, and Nato has not confirmed the air strikes.
A Russian envoy is due to hold talks with the Libyan government in Tripoli as part of attempts to mediate in the conflict.
The envoy, Mikhail Margelov, last week met rebel representatives in Benghazi.
He is faced with a knotty diplomatic challenge, says the BBC's Middle East editor Jeremy Bowen in Tripoli.
Col Gaddafi's government has said it would accept a ceasefire and political talks on the future of the country, but only if the Libyan leader is allowed to keep his position.
The hawkish end of Nato - led by France, UK and US - has been equally clear in its desire for regime change, our correspondent says; Col Gaddafi has to go, these countries maintain, and only then will they talk about a ceasefire and what comes next.
The Gaddafi regime may try to exploit the mixed signals coming out of Nato, our correspondent adds. Some Nato members, notably Germany, believe the military intervention in Libya's civil war was unwise.
But on Wednesday the UK Prime Minister David Cameron insisted the mission could be sustained as long as was needed.
"Time is on our side," he told British lawmakers.