The troops searched buildings for booby traps and snipers as they made their way through the city.
The forces, aligned with Libya's unity government said Friday (June 10) that they had taken control of Sirte, making further gains in Islamic State's North African stronghold.
ISIS Militants in Sirte in Libya
Brigades largely composed of fighters from Misrata advanced this week into the perimeter of Sirte's city center, after launching a counter attack against Islamic State (ISIS / Daesh / ISIL) last month and driving the militant group back along the coastal road between the two cities.
The brigades are part of an operation backed by Libya's U.N.-backed Government of National Accord (GNA), which arrived in Tripoli in March and has been gradually working to establish its authority.
Western powers see it as the best bet for trying to unite Libya's political and armed factions against Islamic State (ISIS / Daesh / ISIL) and for restoring some stability to the oil-rich North African country.
A source from the operations room in Misrata said fighters from the front line in the south of Sirte had looped round to the seafront to capture the port, which lies about 5 km (3 miles) east of the city center.
The brigades have advanced more swiftly than many expected, though their progress has been hampered by suicide bombers, mines and snipers.
More than 100 fighters from the GNA-backed brigades have been killed and more than 500 wounded since the campaign to recapture Sirte began in early May.
Islamic State (ISIS / Daesh / ISIL) started expanding into Libya in 2014 as the political turmoil and conflict in the country worsened.
It took full control of Sirte last year, but has struggled to retain territory or win support elsewhere in Libya.
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