Libyan rebels begged for international help today as Muammar Gaddafi exploited the West's indecision by stepping up his attacks.

As his forces gained momentum, the rebels criticised the West for failing to come to their aid.

"People are fed up. They are waiting impatiently for an international move," said Saadoun al-Misrati, a rebel spokesman in Misrata, the last rebel-held city in the west, which came under heavy shelling.

"What Gaddafi is doing, he is exploiting delays by international community. People are very angry that no action is being taken against Gaddafi's weaponry."

The breakdown of rebel defences in Ajdabiya, 480 miles south-east of Tripoli, threatened to open the gateway to the long stretch of eastern Libya that has been in the control of the opposition throughout the month-long uprising.

Its fall would allow regime forces to bombard Benghazi, Libya's second largest city and the de facto capital of the opposition, by air, sea and land.

Gaddafi's forces continued shelling the city of 140,000 people overnight and throughout the morning with relentless artillery fire and little resistance from the rebels.

An activist hiding out in the city said the rebels were lightly armed but still managed to ambush a group of regime troops marching into the city on foot, but the victory was short lived. Artillery shelling was continuing, he said.

"Ajdabiya is witnessing unprecedented destruction. This is the end of the city," he said.

Residents fled either to tents set up outside the city or 140 miles away to Benghazi.

"The shelling hasn't stopped since last night. The residential areas are under attack," the rebel said, adding that the hospital had been overwhelmed and many of the injured had to be taken to Benghazi.

The city was besieged from the west, where Gaddafi's brigades were deployed from his stronghold of Sirte, and from the north with a warship in the Mediterranean.

"The city is sealed off from the south, from the west and the northern Zwitina port by a warship," he said.

Libyan state television broadcast calls for the opposition to stop fighting, apparently hoping to sway populations in the east away from support of the rebels.

Ajdabiya has been a key supply point for the rebellion, with ammunition and weapons depots. Until now, the Gaddafi forces' offensive toward the east has battled over two oil ports on the Mediterranean, and Ajdabiya is the first heavily populated city in the area they have tried to retake.

It was a major setback to the rebels, who less than two weeks ago were poised to march on Tripoli, the capital, and had appeared capable of sweeping Gaddafi out of power, inspired by successful uprisings in Egypt and Tunisia.

But the regime's better armed and organised military has reversed the tide as efforts led by France and Britain to create a no-fly zone to protect the rebels foundered.

Gaddafi warned rebels: "There are only two possibilities: Surrender or run away."

He said he was not like the Tunisian or Egyptian leaders who fell after anti-government protests. "I'm very different from them," he said. "People are on my side and give me strength."

Gaddafi addressed supporters in Tripoli late last night, calling the rebels "rats" and blasting Western nations. "They want Libyan oil," he said.

Gaddafi's forces also launched an attack on Misrata - which for days has been under a punishing blockade, its population running out of supplies.

The barrage came a day after the government recaptured the last rebel-held city west of Tripoli, solidifying his control over the coastline from the capital to the Tunisian border.

Europe and the United States, meanwhile, were tossing back and forth the question of whether to impose a no-fly zone that the opposition has pleaded for.

Top diplomats from some of the world's biggest powers deferred to the UN Security Council to take action against Libya, as France and Britain failed to win support for a no-fly zone in the face of German opposition and US reluctance.

France said the Group of Eight agreed that a new UN resolution should be adopted by week's end with measures to help Libyan rebels.

A UN resolution introduced yesterday includes no-fly provisions. It also calls for increased enforcement of an arms embargo and freezing more Libyan assets.

One diplomat said the Security Council will be looking to see whether members of the Arab League, which is pressing for the no-fly zone, are ready to seriously participate in the establishment and operation of a zone.