|Forces loyal to Gaddafi have increased attacks in an attempt to retake areas controlled by opposition groups
Muammar Gaddafi, the Libyan leader, has launched a fresh military offensive to retake some of the towns he lost control over the past 18 days.
Opposition to his decades-old rule has quickly swelled into a full-blown rebellion, but Gaddafi stepped up attacks on Friday. By Saturday morning, his forces broke through opposition defences in the city of Az Zawiyah after they began renewed attacks at 6am local time, eyewitnesses told Al Jazeera.
The loyalist forces attacked residential areas in the city, firing heavy artillery from all sides, including from the sea. Tanks and armoured vehicles had broken through defences into Martyrs' Square, in the heart of the town, early in the day.
By 10am, the people of the town had retaken Martyrs' Square, after hours of intense fighting and a high number of casualties. At least 30 people were killed in fierce clashes in the town the previous day, but the death toll from the assault on Saturday morning was unclear.
But Gaddafi's forces had encircled the town and were closing in on the centre again. By midday, they had blocked off all access to the town, the Reuters news agency reported.
"Az Zawiyah is encircled by Gaddafi's forces, there are a lot of checkpoints. They are tightening their grip on the centre," a Reuters journalist said, adding government forces were manning checkpoints some 3km from the centre of town.
Dr Hamdi estimated more than 150 people had been injured on Saturday morning.
"A large number of people are gathered in the centre of the square after they pushed forces out of the city," Dr Hamdi told Al Jazeera.
Thousands of people were assembled at the square, he added, preparing to defend it from any further assaults by Gaddafi's forces.
"There is news that the [pro-]Gaddafi security forces are gathering at the outside of the city and we are bracing ourselves for another attack," Dr Hamdi said.
Others called for foreign intervention to prevent further loss of life.
"There is a very tragic situation in the city," Ahmed, a resident of Az Zawiyah, said. "We were expecting the world to intervene but they have let us down."
"It's not a matter of oil or gas being taken out of our country, it's human lives," he said, pleading for the United Nations or the Arab League to step in to protect Libyan civilians.
"They have no mercy on civilians; the regime is attacking everything indiscriminately," Ahmed said.
Gaddafi's security forces were using ambulances to kidnap wounded people, Human Rights Solidarity, a Geneva-based organisation, told Al Jazeera.
"Now with all the artillery, tanks and armored vehicles, the fierce fighting is ongoing and people are massacred in a way that we didn't see in Iraq,” Abdul-Fatah Az-Zawi, another local, told Al Jazeera.
The opposition has wrested the entire eastern half of the country from Gaddafi's grip, along with several cities in the west close to the capital Tripoli, which is now symbolic to his defiance.
In the past few weeks, the opposition forces were able to fend off several assaults on the territory they control.
Members of Gaddafi's government, diplomats, soldiers and even some of his closest allies have renounced their allegiance, and foreign leaders are becoming increasingly vocal in their calls for the besieged leader to step down.
Anti-Gaddafi protests had been planned on Friday afternoon in the capital, but Al Jazeera's Anita McNaught reported that security personnel were out in force in sensitive parts of the city, and quickly surrounded people who appeared likely to demonstrate.
"Tripoli itself is a city almost completely locked down, electronic communications cut off for the previous 24 hours, shops shut, particularly nobody on the street," she said.
Meanwhile, rebels claimed control of the strategic town of Ras Lanuf, after exchanging heavy shelling and machine gun fire with pro-Gaddafi forces on Friday.
There was no sign of soldiers loyal to Gaddafi in the town on Saturday, although the Gaddafi government's denials that the opposition controlled Ras Lanuf.
Rebel fighters opened fire on a helicopter flying overhead on Saturday, according to the Reuters news agency.
At least eight people were killed and more than 20 wounded during the fighting on Friday, a doctor said.
It was unclear what the rebels would do following the battle in Ras Lanuf. The next major town along the coastal road to the west is Sirte, Gaddafi's home town.
The fighting underlined how both sides are pushing against the deadlock. Both sides are struggling to take new territory, Al Jazeera’s Jacky Rowland reported.
"The situation in the east of the country is really a stalemate, with anti-Gaddafi forces either unable or unwilling to advance further to the west and to try to take the fight closer to Gaddafi's strongholds like Sirte and Tripoli," she said.
"If you look at the rebel forces, they're a rather undisciplined, orderly bunch," she said.
For many of the anti-Gaddafi fighters, this is their first military experience.
Tarik Yousef, dean of the Dubai School of government, told Al Jazeera that foreign powers are likely to be trying to assess the new dynamics that have emerged in the wake of the transformative changes that have rocked the country in recent weeks.
"Effectively, Libya is now a failed state, with two divided geographies," he explained.
Not to be outdone on the diplomatic front, Gaddafi's government on Friday asked that Ali Abdussalam Treki, a senior Libyan diplomat, be accepted as the country's new envoy to the UN after the entire Libyan delegation in New York backed the pro-democracy protesters.
Gaddafi's government made its first official reaction to sanctions announced by the UN, in a letter by Mussa Kussa, his foreign minister.
The letter called for the travel ban and assets freeze ordered against Gaddafi and his close aides "to be suspended until such time as the truth is established".
Kussa demanded that the Security Council "stand up to the states that are threatening force against it."
The foreign minister added that military action against Libya would be "inconsistent" with the UN charter and international law and "compromise a threat to peace and security in the region and indeed the whole world."
Western powers say they are studying a no-fly zone against Libya to prevent attacks on civilians. Yet diplomats say that no official request for such action has been made to the UN Security Council.