Libyan TV showed heavy damage from the strikes, including damage to several structures at Gadhafi's compound in Tripoli. There were no immediate reports on casualties.
NATO warned for days it would increase the intensity of a campaign to oust Gadhafi after more than 40 years in power.
The strikes shook the ground and sent plumes of smoke across Tripoli.
In late afternoon and as the strikes continued, Libyan state television broadcast an audio address from Gadhafi, who denounced NATO and the rebels challenging his rule. He vowed never to surrender.
"We will not kneel!" he shouted. Some 6,850 people, nearly all of them Libyans, have streamed across the border from Libya to Tunisia since Monday to flee the NATO raids as well as fighting between the rebels and government forces, according to the Tunisian Defense Ministry.
It couldn't be confirmed whether Gadhafi's some 10-minute speech was a live phone call or an audio recording, but it appeared to take state television by surprise. The sound was hastily adjusted to make it louder
"We will not surrender: we only have one choice - to the end! Death, victory, it does not matter, we are not surrendering!" Gadhafi said. Highlighting his anger, he called the rebels "bastards."
The Associated Press contributed to this story