ISIS overran the city last year, turning it into a public execution hotbed

Seven bodies found in mass grave on farmland in the west of the city

Three prisoners said to have been found in 'dire humanitarian conditions'

The discoveries were made in the Lybian city of Sirte, an ISIS stronghold

A mass grave and secret prison used to abuse hostages captured by Islamic State has been unearthed in Lybia.

The discoveries were made during an ongoing battle between troops and ISIS militants in the city of Sirte as the fight for liberation continues.

Seven bodies were found buried in the grave that was discovered in a farm west of the city, while three prisoners - in dire condition after months of captivity - were saved when security forces came across a secret prison in another town after it was re-captured from the militants.

Forces loyal to Libya's UN-backed unity government are seen here during clashes with jihadists of the Islamic State on the western outskirts of Sirte where the mass grave and secret prison were found

The Libyan coastal town of Sirte, home town and last stand of Col Muammar Gadaffi, has been destroyed in the fighting

Having claimed Sirte as one of its strongholds last spring, the battle to cleanse the city of IS militants has continued to progress through government forces

The prisoners had been in the secret prison for several months and were found in dire humanitarian conditions, an anonymous source told The New Arab.

Having claimed Sirte as one of its strongholds last spring, the battle to cleanse the city of IS militants has continued to progress through government forces.

Last week, fighters allied to the Government of National Accord encircled IS in the Ouagadougou conference centre – a huge building the group has made as its headquarters.

"Fighting is ongoing around the presidential palaces close to the port and at the Ouagadougou conference centre," the spokesman for the anti-IS operation, Mohammad al-Ghasry, told The New Arab.

"Ground troops are working in conjunction with snipers, while artillery and the air force are bombarding the conference centre and the neighbouring district. We have almost taken back the whole of Sirte," he added.

Soldiers prepare to fight in Sirte (file image) - ISIS took control of Sirte last Spring - the capital of the terrorist group's three self-styled Libyan provinces

Since ISIS overran the city last year, nearly 200 anti-terror fighters have been killed and more than 600 have been injured.

The Islamist terror group took control of Sirte last Spring - the capital of the terrorist group's three self-styled Libyan provinces.

While many civilians have fled, the number of fighters in the area has escalated from 3,000 to as many as 6,500 in just over three months, according to the UN and the Pentagon.

It's said the recruits come via the desert road from Khartoum but only 30 per cent are Libyans.

The rest are Arabs as well as men Chad, Niger, France and India.

Initially when ISIS tightened their grip on the region in 2015 they left the locals to their own devices and kept their distance.

Public killings have become a regular occurrence, with the dead - either shot or beheaded - strung up, or left to hang on ropes from beneath a bridge on the south side of Sirte

New legislation banned smoking and music, closed women's cosmetic shops, made the face-covering niqab compulsory for women and taxes were enforced across a wide range of businesses such as property rental and farming.

But while people were flogged or fined, executions were uncommon.

However in autumn last year more oppressive enforcement began following the arrival of an Isis leadership cadre from Iraq and jihadists confronted leaders from the city’s Salafi community and hostile members of the local al-Furjan tribe.

Public killings have become a regular occurrence, with the dead - either shot or beheaded - strung up, or left to hang on ropes from beneath a bridge on the south side of Sirte.

Many families suffer the same woe when they are prevented from collecting the body of their murdered relative.