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 Col. Qadhafi’s forces, which are trying to crush the nearly five-week-old rebellion against him.

Jets from an international force launched missions over Libya on Saturday, hours after Muammar Qadhafi dispatched troops, tanks and warplanes to the heart of the five-week-old uprising against his rule in a decisive strike on the first city seized by rebels.

Crashing shells shook buildings, and the sounds of battle drew closer to the centre 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.

Earlier on 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 galvanised 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 centre, tank fire drew closer and rebel shouts rang out.

At a news conference in the capital, Tripoli, the government spokesman read letters from Mr. Qadhafi 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 Mr. Sarkozy, British Prime Minister David Cameron, and U.N. Secretary-General Ban Ki-moon.

To Mr. 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 Mr. Qadhafi's forces — broke a ceasefire called by the government.

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 on Saturday.

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 thir-—largest city and the last held by rebels in the west, came under sustained assault well after the ceasefire announcement, according to rebels and a doctor there.

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