Yayha El Mugasabi drove across the front line Wednesday in a white pickup truck topped with a large machine gun. It was 1:30 p.m., and the rebel fighter had arrived from the direction of Ajdabiya, a strategic eastern city under siege by Moammar Gaddafi’s forces.

“A few of their tanks are down the road,” said Mugasabi, smiling feebly at his comrades clustered around a barricaded checkpoint.

Ajdabiya was less than 10 miles away. Behind them: Benghazi, the rebel stronghold. This was the first time Gaddafi’s loyalists had positioned their tanks along the main road connecting the two cities, effectively splitting the rebel forces in two.

For the fighters and civilians crossing this front line, there was anger and fear mixed with determination. They carried stories of violence and fierce fighting underway in Ajdabiya, and a sense that Gaddafi’s forces were edging toward suppressing a rebellion that began with much promise of ousting the 68-year-old leader.

“Where is the international community?” demanded Zaid Al-Libi, who described himself as a military adviser and used a nom de guerre. “There is only God.”

Gaddafi’s troops coming from the west had blocked parts of Ajdabiya and were barring entry from the northeast, Libi and others said. Rebel forces had engaged in fierce fighting with Gaddafi loyalists, who stormed the city Tuesday before withdrawing to the outskirts.

Ajdabiya, a city of 170,000, is the last line of defense before Benghazi, the cradle of the populist uprising that seeks to end Gaddafi’s 41-year rule.

“They started at the western gate to the city, then encircled Ajdabiya and arrived at the eastern gate,” Libi said. “Gaddafi’s forces are now near the eastern gate.”

Along the road from Benghazi to Ajdabiya, the rebels appeared to be preparing for a possible offensive by Gaddafi’s forces in Benghazi. Three rebel tanks, each roughly a mile apart, were parked along the road, their turrets pointed in the direction of Ajdabiya. Rebel fighters congregated at towns along the way, some waiting for orders, others about to head back to Benghazi or return toward the front line in Zuwaytinah and beyond.

In the distance, the heavy thuds of bombardment could be heard. Civilians and fighters said Gaddafi’s forces had barraged Ajdabiya with artillery and rockets Tuesday evening and Wednesday morning. Gaddafi’s forces appeared to be deploying tactics similar to those they had used to capture other rebel-held towns: a combination of shelling and raiding urban areas, engaging in firefights, then retreating to the outskirts of the town at night.

About 1:45 p.m., Idriss Mohammed Adem, 19, a student, crossed the front line with two friends who were just as frightened as he was.

They were headed into Ajdabiya when, they said, gunmen at a checkpoint ordered them to stop. Adem and his friends waved the flag of Libya’s former monarchy, which has been adopted by their revolution. The gunmen fired at their car. They were Gaddafi loyalists. They beat the students and shoved their faces in the sand with their boots.

Then they ordered them to return toward Benghazi, toward the rebel front line, with a message. “They took our cellphones and ordered us to tell you, ‘We are coming with 10,000 soldiers,’ ” Adem said as rebel fighters listened.

Moments later, a fighter named Tarbah pulled aside this journalist and whispered: “He’s a spy. He just came here to scare us. We don’t believe him.”

Tarbah, who declined to give his full name, also had escaped Ajdabiya. He said he saw Gaddafi’s tanks enter the city and at least a dozen soldiers. His commanders, Tarbah said, ordered him to withdraw. “You can’t stop tanks with 40mm machine guns,” he said.

Tarbah and other fighters said Gaddafi loyalists in civilian clothes also emerged from houses and started to attack them. “We didn’t know who was with us and who was against us,” he said.

As he spoke, another car drove across the frontline from the direction of Ajdabiya, carrying a family and its belongings.Muftah Mohammed Showai, 30, a fighter, said seven of his comrades were killed Tuesday when Gaddafi’s forces entered the city.

In interviews, civilians and fighters said they saw people killed or injured inside the city, trapped in the crossfire. Artillery and tank fire, as well as rockets, shattered many houses, they said.

“They surprised us,” said Showai, speaking from a hospital bed in Benghazi.

In another ward lay Zaidan Wahid Hasouny. He, too, crossed the front line late Tuesday — in an ambulance. He was sitting in his neighbor’s car at a gas station in Ajdabiya when one of Gaddafi’s tanks fired, hurling the car into the air. His neighbor was killed instantly.

Despite the odds, many fighters along the front line said they were prepared to die to prevent Gaddafi’s forces from seizing Ajdabiya. “Tonight, we will fight them inside the city,” Libi vowed.