18 September 2011 Last updated at
The Libyan port city of Sirte is Col Muammar Gaddafi's birthplace and one of the last holdouts of pro-Gaddafi loyalists.
It lies half-way along Libya's long coastal road between the capital, Tripoli, and the eastern city of Benghazi, long the base of the rebels fighting to end Col Gaddafi's rule.
Once a little-known fishing village, it was promoted and developed under Col Gaddafi into a second capital with a population estimated at 100,000.
In particular, observers have highlighted Col Gaddafi's promotion of two local tribes - his own Qadhadfa tribe and the Magariha - as reason to believe they could mount a fierce defence of Sirte on his behalf.
They may be aided by the fact that Col Gaddafi made Sirte an important military hub.
Gardabya airport, 16km (10 miles) south of the city, hosts a Libyan air force squadron; the city is home to a large army garrison; and the Houn military base, 240km (150 miles) south, is linked to Sirte by road and air.
The air base has some 50 hangars made of reinforced concrete of the kind normally used to protect fighter planes, according to satellite images analysed by Reuters news agency.
As in other Libyan cities, Col Gaddafi maintained a personal compound in the area.
Even before anti-Gaddafi fighters began their attack on the city, Nato bombers had carried out a number of air strikes there.
Sirte began as a relatively minor stopping post on the coastal road, with no industry, little agriculture and a largely nomadic hinterland.
In facts: Sirte
Birthplace of Libyan leader Muammar Gaddafi
Port city 450km (280 miles) east of Libya's capital Tripoli
Halfway along Libya's northern coast between Tripoli and rebel stronghold of Benghazi
Home to some ministerial offices as Col Gaddafi tried to transfer more authority
Population estimated at 100,000
Col Gaddafi was born in a tent nearby. His nomad parents sent him to primary school in Sirte, and he lavished attention on the city after seizing power in 1969.
During more than four decades in power, he built it into a major hub with a decent infrastructure, university, high-rise buildings and a satellite town.
Its port facilities also became more important with the development of offshore oil extraction.
There have been reports that thousands of mercenaries from Chad, who served in Col Gaddafi's Islamic Arab Legion in the 1980s, retired to Sirte.
Looming over the city is the grandiose Ouagadougou conference centre, where Col Gaddafi hosted fellow heads of state in marble-clad halls.
A tent complex on the beach - likely built from the mobile, highly sophisticated and protected tents that Col Gaddafi used elsewhere - was used to entertain favoured visiting dignitaries.
Col Gaddafi talked of turning Sirte into the capital, ordering all ministries except the foreign service to move their headquarters there.
In practice, however, most civil servants remained in Tripoli.
But Sirte was the site of the foundation of the African Union in 1999. The Sirte Declaration, as it became know, was a proud achievement for Col Gaddafi, an keen promoter of pan-Africanism.
In recent days there have been reports of negotiations between the rebel National Transitional Council (NTC) and dignitaries and clans in Sirte, amid efforts to resolve the fate of the city peacefully.
But the rebels have also been building up their forces to confront Gaddafi loyalists they say are blocking their way to Sirte.
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In pictures: Sirte battle
Images from the Libyan city of Sirte, where transitional government forces have been battling Gaddafi loyalists.
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