Forces loyal to Libya's UN-backed unity government said Saturday that they had seized the port of Sirte, marking a major advance in their offensive to retake the strategic city from the extremist militia.
The forces took control of the port on Friday following fierce clashes with the militants, and then repelled jihadists as they tried to reach the area again on Saturday, an allied media centre said.
The port is located around 5 kilometres from of the centre of Sirte. The city, around 450 kilometres east of the capital Tripoli, is considered critically important because it links Libya's east and west.
The government's allies are fighting street battles against Islamic State militants inside Sirte, Dubai-based broadcaster Al Arabiya reported, citing a pro-government commander.
United Nations envoy for Libya, Martin Kobler, hailed the military advance.
"Impressed by the rapid progress of GNA loyal forces against #daesh in Sirte," the German diplomat said in a tweet, using another name for the extremist gorup.
Last month, the pro-government forces, mainly from the western city of Misrata, began an onslaught to drive Islamic State from Sirte, which the radical group captured last year.
In the past few days, the forces made major territorial gains around and inside Sirte, the biggest city held by Islamic State outside Iraq and Syria.
Libya has been in turmoil since the 2011 revolt, which toppled long-time dictator Moamer Gaddafi.
Islamic State has taken advantage of the chaos to seize territory along the sparsely populated central coast.
The national unity government, formed under a UN-sponsored peace deal, arrived in the capital Tripoli in March amid international hopes it will be able to re-establish stability and stop Islamic State's expansion in the oil-rich country.