ISIS has severely damaged yet another wonder of the ancient Syrian city of Palmyra, this time the 2,000-year-old Temple of Bel.

That's according to the Syrian Observatory for Human Rights, a group monitoring the conflict, citing contacts on the ground.

It was feared Bel would be next on the militant's hitlist at the Unesco World Heritage Site in central Syria after the temple of Baal Shamin was dynamited last week.

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The Temple of Bel at Palmyra has apparently been blown up by ISIS in the latest atrocity committed by the group at the ancient city

The temple of Baal Shamin is destroyed by ISIS. It has been suggested the group could take Palmyra apart piece by piece

Palmyra, 215 kilometres northeast of Damascus, was a jewel of the ancient world and is revered because its Greco-Roman ruins are so well preserved

Dedicated to the Phoenician god of storms and fertilizing rains, the UN called the destruction of Baal Shamin a war crime.

A Palmyra resident, who goes by the name of Nasser al-Thaer, said IS militants set off a huge blast at 1.45 pm on Sunday.

'It is total destruction,' he said of the scene of the explosion. 'The bricks and columns are on the ground.'

'It was an explosion the deaf would hear,' he added.

The resident said only the outer wall surrounding the Temple of Bel remains.

Constructed in 32AD, the temple was dedicated to gods worshipped by the Semites - a group of different cultures in the Ancient Middle East including Assyrians, Phoenicians, Hebrews and Arabs.

It stood on an artificial hill which dates back more than 2,200 years and lavish carvings of the then-known seven planets, zodiac signs and Makkabel the fertility god adorn the monolithic ceiling of its northern chamber.

The remains of a basin, altar and even a dining hall can be made out inside the temple. On the north-west corner is a ramp where sacrificial animals were once led into the building.

ISIS has already destroyed the Temple of Baal Shamin, the Lion of al-Lat and several statues in the city of Palmyra and as now hit the Temple of Bel (bottom right)

The Temple of Baal Shamin was dynamited last week. Dedicated to the Phoenician god of storms and fertilizing rains, the UN called the destruction a war crime

ISIS posted a propaganda video showing its fighters loading up the Temple of Baal Shamin with exposives

ISIS also destroyed the treasured Lion of al-Lat – the 15-tonne, 3.5m-high piece made out of limestone early in the 1st Century AD.

The lion was considered the ancient consort of al-Lat, the goddess of the underworld who abhorred violence.

Stood in front of the ruins of the Temple of al-Lat, it symbolised her anger towards at anyone spilled blood in the city.

Dr Robert Bewley, Project Director at the School of Archaeology at Oxford, has predicted Palmyra will be razed to the ground 'monument-by-monument' by ISIS to wring every last propaganda opportunity out of the destruction.

He claimed the terror group is determined to destroy Palmyra piece by piece, known as 'the oasis in the desert' was a jewel of the ancient world and is revered because its Greco-Roman ruins are so well preserved.

Dr Bewley told MailOnline this week: 'One fear is that ISIS will do piecemeal damage over the coming weeks to keep the publicity machine running, so it will be a slow but equally destructive approach.'

Islamic State took over Palmyra in May and this propaganda image reportedly shows 25 Syrian government soldiers kneeling in front of what appears to be children or teenagers wearing desert camouflage in the ancient amphitheatre

Already destroyed is one of Palmyra's most iconic relics, the Lion of al-Lat, which acted as a guardian for the goddess of the underworld

Unesco describes Palmyra as a heritage site of 'outstanding universal value'.

ISIS fighters view such sites as targets because of their desire to wipe out all traces of 'non-Islamic' history and what they regard as the idolatrous antiquities, icons and carvings.

Islamic State has imposed a violent interpretation of Islamic law across its self-declared 'caliphate' straddling Syria and Iraq.

It already has blown up several sites in neighboring Iraq, and it is also believed to be selling looted antiquities.

The group took over Palmyra in May and last week murdered retired archaeologist and scholar Khaled Asaad, 82, who worked for more than 50 years as head of antiquities there.

Earlier Sunday, IS fighters pushed into a large district in southern Damascus, clashing with rival militants just a few kilometers from the center of the Syrian capital, the extremist group and Syrian activists said.

More than two dozen militants were killed in the clashes on the edges of the Qadam neighborhood, said the Observatory.

The 82-year-old director of antiquities and the museum in Palmyra, Khaled Asaad, was murdered by ISIS last week

The pro-IS Aamaq News Agency reported that IS fighters seized half of Qadam. The Observatory's Rami Abdurrahman said IS fighters were holding two streets and that fighting was continuing.

IS supporters posted propaganda pictures claiming to show IS fighters advancing in the narrow streets of Qadam. The authenticity of the images could not be confirmed independently.

IS has emerged as one of the most powerful forces in the battle to overthrow Syrian President Bashar Assad. Armed Islamic factions fighting forces loyal to Assad control parts of Damascus and large parts of the city's suburbs.

IS fighters control large parts of the Palestinian refugee camp of Yarmouk, east of Qadam.

Also Sunday, a mortar round hit an upscale neighborhood of central Damascus, killing four people, including a girl, Syrian state TV said.

It is not uncommon for Damascus to be shelled. Sunday's attack targeted the posh neighborhood of Abu Rummaneh, which houses hotels and several embassies.