Revolutionary fighters assaulted Moammar Gadhafi's hometown from all sides Friday in what they hope will be a final all-out offensive to crush resistance in the most important bastion of regime loyalists.
Libya's new leaders say Sirte's fall is critical to formally declaring liberation and setting a timeline for elections — even if fighting persists elsewhere and the ousted leader is nowhere to be found — more than six weeks after the then-rebels seized control of the capital and most other parts of the country.
The two sides battered each other with rockets, mortar shells and tank fire, as Gadhafi snipers fired down on fighters advancing through housing complexes. Friday's push marks the largest new assault on the city for weeks.
Smoke drifted over the skyline and explosions thundered throughout the city, as long lines of residents fleeing by car formed at revolutionary forces' checkpoints.
Fighters entering through the western gate on Friday quickly advanced to within just a mile (two kilometers) of the city center but faced heavy resistance from a loyalist force of roughly 800 men, according to one commander's estimate.
"We started the attack at 6 a.m. today. The first group hit the outskirts of Sirte. We were fired on by Gadhafi snipers. We had many soldiers wounded," said commander Altaib Aleroebi of the ex-rebels' West Mountain Brigade, which led the attack on the western front.
Thousands of civilians have fled Sirte as fighting intensified, describing an increasingly desperate humanitarian situation. Many were caught off guard by Friday's assault and fled in panic as explosions boomed around the city.
Gadhafi loyalists who pulled back to Sirte when they lost control of other cities are putting up fierce resistance.
At least 12 revolutionary fighters were killed and 195 were wounded, doctors said. Ambulances sped down Sirte's main avenue to a field hospital set up in an abandoned villa five miles (eight kilometers) from the center. Doctors said a senior commander, Ali Saeh of the Free Libya Brigade, was injured, shot twice by a sniper as he led fighters through loyalist forces in a residential area.
"We are receiving many gunshot wounds, mostly to the head, neck and chest from sniper fire. We have received many injured today," Dr. Ahmed Mohammed Tantoun said Friday, adding he expects many more injured fighters to arrive through the day as fighting intensifies.
Medical workers tried to save an unresponsive woman. A child with a wounded leg sat on the floor. A helicopter landed near the hospital to carry some of the wounded to hospitals in Misrata, which lies west of Sirte.
Meanwhile, a U.S. administration official, speaking on condition of anonymity to discuss intelligence matters, said that 80 percent of the city was now pacified or under the control of the transitional government. The official said the remaining area might take a little more time as forces move methodically to eliminate the resistance.
At a checkpoint near the field hospital, NTC fighters checked dozens of cars carrying families fleeing Sirte.
"We didn't know there was going to be an assault," said Saeed Ramadan, whose vehicle had shrapnel holes and a broken window. "I couldn't sleep last night, there was very heavy shelling. I was afraid for my kids and had to get them out."
A Sirte resident who gave his name as Abdel Nasser said: "Last night there was heavy random firing and shelling. We had a hundred narrow escapes. Conditions are tragic. You can smell the rotting corpses at the hospital."
Concerns about the humanitarian crisis have focused on the Ibn Sina hospital in the city. Medical workers who fled Sirte say patients were dying on the operating table because there was no oxygen and no fuel for the hospital's generators.
Hassan Briek, another fleeing resident, said fewer than half of Sirte's residents remained in the city and most had moved to three neighborhoods where there has been less fighting.
"There are lots of families in those districts of the city," Briek said. "No one knew there was going to be an assault today. No one is sleeping. Food isn't the problem. It's the shelling."
Gadhafi and several of his sons are still at large more than seven weeks after rebel fighters stormed the capital, Tripoli, and ended his rule.
De facto Prime Minister Mahmoud Jibril said on Thursday that Gadhafi was hiding in southern Libya under the protection of tribes, crossing occasionally into Niger, and government forces expected to pinpoint his whereabouts soon.
An audio recording of Gadhafi obtained by Reuters on Thursday from Syria-based Arrai television was the first sign of life from him since September 20, when the same station last aired a speech by him.
"If the power of (international) fleets give legitimacy, then let the rulers in the Third World be ready," Gadhafi said in an apparent reference to NATO's support for NTC forces.
"To those who recognize this council, be ready for the creation of transitional councils imposed by the power of fleets to replace you one by one from now on."
Reuters and The Associated Press contributed to this report.