NATO planes hit Libya hard Tuesday, attacking the city of Tripoli at least 40 times in rare daytime strikes.

NATO is pressuring Libyan leader Moammar Gadhafi to resign. The morning air raids shook the ground in a series of sharp explosions.

As the strikes continued through the afternoon, Libyan state television aired an audio address from Gadhafi, who denounced NATO and rebels in the country for challenging his rule.

"We will not kneel!" he shouted.

Forces were likely targeted a military barracks near Gadhafi's central tripoli compound.

NATO officials warned for days they were increasing the intensity of their two-month campaign to oust Gadhafi.

Some 6,850 people have fled across the border from Libya to Tunisia since Monday to flee the NATO raids and fighting between protestors and government forces, according to the Tunisian Defense Ministry.