ZUWAYTINAH, Libya – Troops loyal to Libyan leader Moammar Gaddafi on Wednesday positioned tanks for the first time along the main road connecting the strategic eastern city of Ajdabiya to the rebel stronghold of Benghazi, effectively splitting the forces opposing Gaddafi in two, according to rebel commanders, fighters and witnesses.

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

Ajdabiya, a city of 170,000 people, 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,” said Zaid Al-Libi, who described himself as a military advisor and used a nom de guerre. “Gaddafi’s forces are now near the eastern gate.”

Other fighters on this front line, about 10 miles away from Ajdabiya, confirmed his assessment on Wednesday afternoon. “A few of their tanks are down the road,” said Yahya el Mugasabi, a fighter who arrived from the direction of Ajdabiya. “We’ve been firing a lot of weapons at each other.”

Along the road from Benghazi to Ajdabiya, the rebels appear to be preparing for a possible offensive by Gaddafi’s forces on 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 headed back to Benghazi or returning towards the front line in Zuwaytinah and beyond.

In interviews, many said they were prepared to fight hard to prevent Gaddafi’s forces from seizing Ajdabiya.

“Tonight, we will fight them inside the city,” predicted Al-Libi.

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

Hundreds of residents, mostly women and children, fled Aj­dabiya Tuesday with whatever they could carry.

Libyan state television asserted that Ajdabiya had “been cleansed of mercenaries and terrorists linked to the al-Qaeda organization,” referring to the rebels.

The assault on Tuesday was the latest sign that the forces that have fueled the Arab spring over the past few weeks are coming under pressure that might prove insurmountable. In Bahrain, the government has declared a state of emergency and invited Saudi troops to quell unrest. In Yemen, police fired bullets and tear gas at protesters on Sunday, a day after security forces killed seven demonstrators in protests across the country.

In Libya, the rebels are up against a military force that is far superior and have been unable to persuade foreign powers to intervene militarily. On Tuesday, recommendations from France and Britain for a no-fly zone over Libya were rebuffed by foreign ministers from the Group of Eight countries.

French Foreign Minister Alain Juppe lamented that Western powers had “missed an opportunity to shift the balance.”

“If we had used military force last week to neutralize some runways and the several dozen airplanes at Gaddafi’s disposal, maybe the reversal that is happening now to the opposition’s disadvantage would not have taken place,” Juppe told Europe 1 radio.

The seizure of Ajdabiya by Gaddafi’s forces would deliver a severe tactical and psychological blow to the rebel movement and bring Benghazi, 99 miles north of Ajdabiya, within their sights. Ajdabiya sits at the nexus of highways that would allow Gaddafi’s forces to either mount a frontal assault on Benghazi or encircle and place a chokehold on it and other pro-rebel cities along the Mediterranean coast.

On the front lines, rebel fighters increasingly accused the movement’s leadership of not providing them with adequate military equipment or experienced officers to lead them, despite public promises by senior commanders.

On Sunday, Abdul Fattah Younis, the head of the rebel armed forces and Gaddafi’s former interior minister, declared that conventional forces, most of them defected soldiers from Gaddafi’s army, were playing a significant combat role.

But they were nowhere to be seen Tuesday on what was perhaps the most pivotal battlefront of the rebellion.

“See the scars on my face. Since the morning, I have been fighting on the front. I am tired,” said Mohammed Gassar, 31, a former water company employee. “Where is the army? We need heavy weapons, we need leadership.”

Others expressed anger at the international community, accusing it of betraying their cause and leaving them to face Gaddafi on their own.

“These politicians are liars. They just talk and talk, but they do nothing,” said Mohammed al-Gunati, 30, a driver who stood behind a machine gun. “Where is America? Where are the Europeans? Even the Arabs, they are all just the same. They keep quiet. They just watch us as we die.”

Minutes later, fighters spotted two reconnaissance planes high in the sky and began to futilely fire their machine guns in the air, wasting scores of bullets.

One fighter looked up and started to pray: “I don’t have help except my God.”

By Tuesday afternoon, with plumes of black smoke rising over the desert from artillery and rockets, convoys of rebel vehicles fled from the front lines, along with ambulances and cars filled with civilians. “I could see them with my own eyes,” said Sherif Layas, 34, a marketing manager-turned-rebel fighter. “They have a big force coming.”

As the bombardment intensified and neared the western edge of the city, some fighters vowed to mount a last stand against Gaddafi’s forces, while others cursed in frustration at their inability to fight their enemy’s superior firepower and military capabilities.

“We can’t use our guns. They have tanks. We have nothing,” screamed a fighter atop a machine-gun-mounted pickup moments after they reached the outskirts of the city. “All we can do is pray to Allah.”

On Tuesday, Libyan government forces took control of two more rebel-held towns. State television showed pictures of Gaddafi’s fighters holding a victory rally in the center of Zuwarah, a small town 76 miles west of Tripoli, and footage of damage caused to vehicles in Brega, west of Benghazi, which had changed hands several times in the past few days.

In the capital, Tripoli, Gaddafi supporters honked their horns, fired automatic weapons into the air and set off fireworks to celebrate government assertions that Ajdabiya had fallen.

In an interview with the Italian newspaper Il Giornale, Gaddafi warned the rebels to “surrender or run away.” He said he was not like the Tunisian or Egyptian leaders, who fell after anti-government demonstrations. “I'm very different from them,” he said. “People are on my side and give me strength.”

Some rebel fighters declared that they would not give up Ajdabiya without a fierce battle, which could involve street-by-street, house-by-house combat. “We can’t fight Gaddafi because of his airplanes and heavy weapons. But if his forces enter this city, we’ll show how we can fight,” said Ali Abdullah al-Shahi, 30, a driver-turned-guerrilla fighter. “We will battle them in the streets until the very last drop of our blood.”

Correspondents Liz Sly in Tripoli and Edward Cody in Paris contributed to this report.