A Red Cross convoy carrying aid to relieve a humanitarian crisis in Libya's besieged city of Sirte had to turn back on Monday because Libyan interim government forces unleashed a barrage of fire.

Government forces on the other side of the city, Muammar Gaddafi's home town, broke weeks of deadlock by pushing into a district of Sirte where their commanders had said they believed one of Gaddafi's sons, Mo'atassem, was hiding.

In Tripoli, the man convicted of the 1988 bombing of a U.S.-bound airline over the Scottish town of Lockerbie told Reuters in an interview his role had been exaggerated and that the truth behind the bombing would emerge soon.

Aid agencies say they are concerned about the welfare of civilians inside Sirte, one of the last pro-Gaddafi bastions left in the country, who are trapped by the fighting and running out of food, water, fuel and medical supplies.

The International Committee of the Red Cross (ICRC) took some supplies into Sirte last week, and it tried again on Monday, assembling a convoy of two trucks carrying aid, and accompanied by two four-wheel drive vehicles.

The convoy set off from a bridge a few kilometres west of Sirte but came to a halt after only about 100 metres because interim government forces started firing into the city.

They fired a heavy barrage of mortar bombs, artillery, rocket-propelled grenades and anti-aircraft weapons just as the convoy was starting to move. The ICRC convoy turned around and headed back west, away from Sirte.

An anti-Gaddafi commander at the scene, Ismail Al-Sosi, told Reuters: The rebels secured the way for the International Red Cross to go but as soon as they entered the city they returned because of the (pro-Gaddafi) militias firing. We did not start the firing. The militias started the firing.

However, a Reuters team who witnessed the incident, said they saw no incoming fire from the Gaddafi loyalists inside Sirte.

Speaking just before the aborted attempt to get supplies into the city, an ICRC official said the humanitarian situation there was dire.

We're trying to provide medical assistance and oxygen to the hospital in Sirte, said Hishem Khadrawy. We are really concerned about the medical situation because of the conflict.

GOVERNMENT ADVANCE

Government forces who had for weeks been pinned down by artillery and rocket fire on the eastern edge of Sirte were able to advance several kilometres into the city, capturing the southern district of Bouhadi.

Commanders with the interim government, the National Transitional Council (NTC), had earlier said they believed one of Gaddafi's sons was in the district.

The army has fled, said NTC fighter Hussein al-Mazeq.

A Reuters reporter at a traffic circle in the centre of Bouhadi said the NTC forces appeared to be in control, though they said there were isolated pockets where loyalists fighters were still holed up.

Government fighters loaded their pick-up trucks with items taken from houses in the district, including carpets and chairs.

On the way in to Bouhadi, the streets were deserted apart from some burned-out cars and tank shell casings. Billboards which had shown images of Muammar Gaddafi were torn down.

A group of NTC fighters headed out of the city on foot carrying a haul of rocket-propelled grenades, Kalashnikov rifles, boxes of ammunition and pairs of new army boots. They said they found them in the homes of Gaddafi supporters.

We took them from Muammar, Allahu Akbar! (God is Greatest), one of the fighters shouted.

LOCKERBIE BOMBING

Abdel Basset al-Megrahi was convicted in a Scottish court over the Lockerbie bombing. He was released two years ago on the grounds that he was suffering from terminal cancer.

Looking frail and his breathing laboured, he spoke from a bed at his home in Tripoli, with medical monitors pinging in the background.

The facts (about the Lockerbie bombing) will become clear one day and hopefully in the near future. In a few months from now, you will see new facts that will be announced, he told Reuters Television.

The West exaggerated my name. Please leave me alone. I only have a few more days, weeks or months.

Al-Megrahi, who had served as an intelligence agent during Gaddafi's rule, denied any role in the human rights abuses committed by the deposed Libyan leader.

All my work was administrative. I never harmed Libyans, he said. I didn't harm anyone. I've never harmed anyone in my life.

Libyans ended Gaddafi's 42-year rule in August when rebel fighters stormed the capital. Gaddafi and several of his sons are still at large and his supporters hold Sirte and the town of Bani Walid, south of Tripoli.

Gaddafi's supporters are too weak to regain power, but their resistance is frustrating the new rulers' efforts to start building the post-Gaddafi Libya.

SIRTE HOSPITAL

At the western outskirts of the city, civilians who were able to get out of Sirte spoke of many other people unable to leave and facing deteriorating conditions.

Boshnab Khalifa drove out of the city with his family. A woman in the back seat of his car clutched a Koran.

We were in our apartment and then the wall was blown in by a rocket, he said. The situation is very bad. Our family and our friends are trapped inside. They cannot get out. There are many families trapped inside, some have no gas for their cars, other (cars) have been damaged or destroyed.

A city of about 75,000 people, Sirte holds symbolic importance. Gaddafi, known for his self-aggrandising gestures, transformed his birthplace from a sleepy fishing town into Libya's second capital.

At his instigation, parliament often sat in Sirte and he hosted international summits at the Ouagadougou Hall, a marble-clad conference centre he had built on a desert plot in the south of the city.

Concerns about the humanitarian crisis have focussed on the city's Ibn Sina hospital. 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.

Medical staff outside Sirte who had treated wounded civilians fleeing the fighting on Monday said they had been told the corridors were full of patients and that treatment was being given only to pro-Gaddafi fighters or members of Gaddafi's tribe.

There is a section for civilians and a section for the (pro-Gaddafi) brigades. They are only treating the brigades and leaving the normal people, one member of an ambulance crew told Reuters. That account was repeated by a doctor at a field hospital near the city.

With Libya's rulers focussing on the battles for Sirte and Bani Walid, a power vacuum has emerged.

The interim government is nominally in charge, but real power on the ground is exercised by armed anti-Gaddafi militias who are jockeying for influence in the new Libya.

The chairman of the NTC, Mustafa Abdel Jalil, announced a minor reshuffle of his team, but kept the crucial portfolios of oil and foreign affairs unchanged.