Machine-gun and heavy-weapons fire has been heard across Tripoli, the heaviest since the rebellion against Muammar Qaddafi began, BBC news reports.

The city has been Qaddafi’s main stronghold as his forces attempt to regain control of the country. To the east, a 30-member National Libyan Council has been formed in the rebel city of Benghazi.

Since 20 February, the Qaddafi regime has lost control along the country’s coastal belt, where most of Libya’s cities and economic infrastructure are located, but has since been winning back ground, according to the US’ Washington Institute for Near East Policy.

Qaddafi’s forces have surrounded the opposition-held industrial city of Zawiyah, which houses an oil refinery and two oil and gas export terminals, only 50 kilometres from Tripoli. The city has sustained numerous assaults since 28 February.  

The nearby coastal town of Sabratha was retaken by the regime on 1 March cutting Zawiyah off from other opposition head enclaves to the west.

Libya’s third-largest city, Misratah, located to the east of Tripoli is fully surrounded and has held out against four major offensives by Qaddafi forces since 21 February.

In the east of Libya, Qaddafi’s forces have also recaptured the town of Sidra and the port of Ras Lanuf, site of Libya’s largest oil refinery and oil export facilities.

The Washington Institute says opposition forces control three refineries in eastern Libya capable of processing 40,000 barrels a day (b/d).

Qaddafi controls the 120,000 b/d Zawiyah refinery along with the 220,000 b/d Sidrah refinery, which are still in operation.

Libya’s total oil output has fallen by almost 50 per cent, according to Shukri Ghanem, chairman of state-owned National Oil Corporation (NOC). The country has the ability to produce about 1.6 million b/d. Most of its oil fields are located in the eastern deserts, which has largely been taken over by the opposition. Oil tankers docking at Tobruk and Benghazi are still being loaded with oil sold before the uprising.

The opposition-controlled Arabian Gas & Oil Company (AGOC), based in Benghazi has continued making shipments and is seeking to establish itself as the legal marketing body for Libyan oil.