Crashing shells shook buildings, and the sounds of battle drew closer to the center of Benghazi, where a doctor said 27 bodies were brought to the hospital by midday. By late in the day, warplanes could be heard overhead.
French President Nicolas Sarkozy said after an emergency summit in Paris that French jets were already targeting Gadhafi's forces. The 22 participants in Saturday's summit "agreed to put in place all the means necessary, in particular military" to make Gadhafi respect a U.N. Security Council resolution Thursday demanding a cease-fire, Sarkozy said.
"Our planes are blocking the air attacks on the city" of Benghazi, he said, without elaborating. French planes have been readying for an attack in recent days.
In an open letter, Gadafhi warned: "You will regret it if you dare to intervene in our country."
Earlier Saturday, a plane was shot down over the outskirts 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.
Before the plane went down, journalists heard what appeared to be airstrikes from it. Rebels cheered and celebrated at the crash, though the government denied a plane had gone down — or that any towns were shelled on Saturday.
The fighting galvanized the people of Benghazi, with young men collecting bottles to make gasoline bombs. Some residents dragged bed frames and metal scraps into the streets to make roadblocks.
Abdel-Hafez, a 49-year-old Benghazi resident, said rebels and government soldiers were fighting on a university campus on the south side of the city, with government tanks moving in, followed by ground troops. In the city center, tank fire drew closer and rebel shouts rang out.
At a news conference in the capital, Tripoli, the government spokesman read letters from Gadhafi to President Barack Obama and others involved in the international effort.
"Libya is not yours. Libya is for the Libyans. The Security Council resolution is invalid," he said in the letter to Sarkozy, British Prime Minister David Cameron, and U.N. Secretary-General Ban Ki-Moon.
To Obama, the Libyan leader was slightly more conciliatory: "If you had found them taking over American cities with armed force, tell me what you would do."
Government spokesman Moussa Ibrahim said the rebels — and not Gadhafi's forces — broke a cease-fire called by the government.
"Our armed forces continue to retreat and hide, but the rebels keep shelling us and provoking us," Musa told The Associated Press.
In a joint statement to Gadhafi late Friday, the United States, Britain and France — backed by unspecified Arab countries — called on Gadhafi to end his troops' advance toward Benghazi and pull them out of the cities of Misrata, Ajdabiya and Zawiya. It also 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.
In Benghazi, crowds gathered at the courthouse that is the de facto rebel headquarters. About 200 people were in the area, drinking tea and talking. Some brought a tank and a mounted anti-aircraft gun they said they had captured today.
Dr. Gebreil Hewadi of the Jalaa Hospital and a member of the rebel health committee said that 27 dead had been taken to the hospital since Friday night.
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.
Foreign Minister Moussa Koussa said that Libyan officials had informed the U.N. and the Security Council that the government was holding to the cease-fire and called for a team of foreign observers to verify that.
"The nation is respecting all the commitments put on it by the international community," he said, leaving the podium before answering any questions about Benghazi.
In the course of the rebellion, Libya has gone from a once-promising economy with the largest proven oil reserves in Africa to a country in turmoil. The foreign workers that underpinned the oil industry have fled; production and exports have all but ground to a halt; and its currency is down 30 percent in just two weeks.
The oil minister, Shukri Ghanem, held a news conference calling on foreign oil companies to send back their workers. He said the government would honor all its contracts.
"It is not our intention to violate any of these agreements and we hope that from their part they will honor this agreement and they will send back their workforces," he said.
Italy, which had been the main buyer for Libyan oil, offered the use of seven air and navy bases already housing U.S., NATO and Italian forces to enforce the no-fly zone over Libya.
Italy's defense minister, Ignazio La Russa, said Saturday that Italy wasn't just "renting out" its bases for others to use but was prepared to offer "moderate but determined" military support.