Libyan government forces captured landmark buildings in a move towards the centre of Muammar Gaddafi's hometown Sirte, but came under a fierce counter attack which inflicted dozens of casualties.
Taking Sirte would bring Libya's new rulers a big step closer to establishing control of the country almost two months after they seized the capital Tripoli, but Gaddafi loyalists are putting up stiff resistance.
National Transitional Council (NTC) forces captured Sirte's main hospital as well as the university and a lavishly built international conference centre.
The university, seized overnight, also came under a sustained counter-attack, as did the conference centre.
One large group of NTC fighters, approaching Sirte from the west and trying to pin down Gaddafi loyalists against the sea, saw their advance turn into a rout under heavy and accurate mortar bombardment.
The speed of the reversal underlines the fragility of government advances and the weight of the task still ahead of them despite their leaders' upbeat assessment of the fight.
NTC chairman Abdel Jalil told a news conference in Tripoli that his men had reached Sirte city centre and were combing the town for snipers.
The only other major Gaddafi-held town, Bani Walid, in the desert far to the south, was also under government siege from no fewer than five sides, he said.
The prolonged struggle to conquer Sirte and the other few remaining bastions of pro-Gaddafi loyalists has sidetracked NTC efforts to set up effective government and rebuild oil production vital to its economy.
Sirte holds symbolic significance because Gaddafi, who ruled for 42 years, turned it from a fishing village into a second capital. He built opulent villas, hotels and conference halls to house the international summits he liked to stage there.
But taking Sirte carries risks for Libya's new rulers. A drawn-out battle with many civilian casualties will breed hostility that will make it very difficult for the NTC to unite the country once the fighting is over.
Thousands of civilians have fled Sirte as fighting has intensified, describing increasingly desperate conditions for those still inside the seafront city.
