Libyan forces struck Saturday at the heart of the rebellion against Muammar al-Qaddafi, shelling the outskirts of the rebel capital and launching airstrikes in defiance of international demands for a halt to the fighting.

Muammar al-Qadhafi called the United Nations resolution authorizing international military intervention in Libya as "invalid."

The Libyan leader says he sent a message to President Barack Obama defending his decision to attack rebel cities: "If you found them taking over American cities by the force of arms, tell me what you would do."

The statement came from the government spokesman at a news conference in Tripoli.

Qaddafi also sent a letter to the French and British leaders, and the U.N. secretary general, saying the resolution violates the U.N. charter and saying they would "regret" any intervention.
"Libya is not for you, Libya is for the Libyans," he said.

Muammar al-Qaddafi called the U.N. resolution "invalid," and sent letters to U.N. and Western leaders.

The announcement came after rebels shot down a warplane Saturday that was seen bombing the outskirts of the key rebel-held city of Benghazi, sending up a massive black cloud of smoke. An Associated Press reporter saw the plane go down in flames and heard the sound of artillery and crackling gunfire in the distance.

The fighting galvanized the people of Benghazi, with young men collecting bottles to make Molotov cocktails. Some residents dragged bed frames and metal scraps into the streets to make roadblocks.

"Where is France, where is NATO?" cried a 50-year-old woman in Benghazi. "It's too late."

Government spokesman Ibrahim Musa denied that a government plane had gone down. He also denied government forces shelled any Libyan towns on Saturday, saying the rebels are the ones breaking the cease fire by attacking military forces.

"Our armed forces continue to retreat and hide, but the rebels keep shelling us and provoking us," Musa told The Associated Press.

Leaders from the Arab world, Africa, the United States and other Western powers were holding urgent talks in Paris on Saturday over possible military action against Qaddafi's forces, which are trying to crush the nearly 5-week-old rebellion against him.

Trying to outmaneuver Western military intervention, Qaddafi's government declared a cease-fire on Friday as the rebel uprising faltered against his artillery, tanks and warplanes. But the opposition has said shells rained down well after the announcement and accused the Libyan leader of lying.

Wary of the cease-fire, Britain and France took the lead in plans to enforce a no-fly zone, sending British warplanes to the Mediterranean and announcing the crisis summit in Paris with the U.N. and Arab allies. In Washington, President Barack Obama ruled out the use of American ground troops but warned that the U.S., which has an array of naval and air forces in the region, would join in military action.

There should be no doubt about the Libyan leader's intentions "because he has made them clear," Obama said. "Just yesterday, speaking of the city of Benghazi, a city of roughly 700,000, he threatened 'we will have no mercy and no pity.' No mercy on his own citizens."

In a joint statement to Qaddafi late Friday, the United States, Britain and France -- backed by unspecified Arab countries -- said a cease-fire must begin "immediately" in Libya, the French presidential palace said.

The statement called on Qaddafi to end his troops' advance toward Benghazi, the rebel headquarters, and pull them out of the cities of Misrata, Ajdabiya and Zawiya, and called for the restoration of water, electricity and gas services in all areas. It said Libyans must be able to receive humanitarian aid or the "international community will make him suffer the consequences" with military action.

Parts of eastern Libya, where the once-confident rebels this week found their hold slipping, erupted into celebration at the passage of the U.N. resolution. But the timing and consequences of any international military action remained unclear.

Misrata, Libya's third-largest city and the last held by rebels in the west, came under sustained assault well after the cease-fire announcement, according to rebels and a doctor there. The doctor, who spoke on condition of anonymity because he feared reprisals, said Gadhafi's snipers were on rooftops and his forces were searching homes for rebels.

"The shelling is continuing, and they are using flashlights to perform surgery. We don't have anesthetic to put our patients down," said the doctor, who counted 25 deaths since the morning.
Libya's deputy foreign minister, Khaled Kaim, denied late Friday that government forces had violated the cease-fire and invited four nations to send observers to monitor compliance: Germany, China, Turkey and Malta.

"The cease-fire for us means no military operations whatsoever, big or small," he told reporters in Tripoli.

He said military forces were positioned outside Benghazi but that the government had no intention of sending them into the city.

The Associated Press contributed to this report.