NATO warplanes shook the Libyan capital Tripoli on Friday with more bombing runs, targeting several parts of the city.

It was not immediately clear what was hit or whether there were casualties. Sirens of rescue vehicles blared through the streets.

NATO has most often struck under the cover of darkness, but daytime assaults have become more common. Friday's raids followed a barrage on Thursday night.

As the attacks continued, there were tentative attempts at resolving the three-month-long conflict.

Libyan leader Moammar Gadhafi's son said his father is willing to hold elections, and that he would step aside if he loses. Rebels and the United States have rejected that offer.

The son, Seif al-Islam Gadhafi, told an Italian newspaper Thursday the vote could take place within three months. He said transparency could be guaranteed by international observers.

An opposition spokesman told al-Jazeera television the time for elections has passed, “because our forces are at the outskirts of Tripoli.” A U.S. State Department official also dismissed the idea.

A Russian envoy in Tripoli told reporters earlier Thursdayi that Libyan officials assured him the government is in direct contact with rebels in their eastern stronghold, Benghazi.

Libyan Prime Minister Baghdadi al-Mahmoudi says Mr. Gadhafi will not relinquish power in response to international pressure for him to step down.