Libyan forces in the final stages of a six-month campaign to recapture Sirte from Islamic State said they freed 14 civilians on Sunday from a residential area where some militants are holding out.

The forces, composed of fighters mainly from Misrata, said they were exercising caution to limit casualties to civilians.

Islamic State took full control of Sirte, a city of about 80000 inhabitants, early last year. Its loss would leave the jihadist group without any territorial control in Libya.

The Libyan forces have the remaining militants in Sirte surrounded in part of the Ghiza Bahriya neighbourhood. The civilians who left on Sunday were Libyans - mainly women and children.

They are the latest of several groups of civilians to escape or be released, many of them migrant women and children who were kidnapped by Islamic State as they tried to make their way through Libya towards Europe.

There was no advance against Islamic State on Sunday, Rida Issa, a spokesman for Misrata-led forces, said. On Saturday, Reuters reporters witnessed heavy tank and howitzer fire against militant positions resulting in small gains.

The forces fighting Islamic State in Sirte are aligned with a UN-backed government in Tripoli, though strategic decisions are taken by commanders in the field and in Misrata. Since August 1, they have been assisted by more than 360 US air strikes.