Isis fighters have shot and killed nine children close to the ancient city of Palmyra, a Syrian monitoring group has claimed.

The UK-based Syrian Observatory for Human Rights (SOHR) said government workers were among those killed by militants rapidly advancing on the Unesco world heritage site.

The SOHR said Isis launched attacks on Tadmur, which is close to Palmyra, on Thursday, leading Maamoun Abdulkarim, Syria's director-general of antiquities and museums, to call for help in protecting the 2,000-year-old city from falling into its clutches.

Extremist Islamic State (IS) militia is advancing towards Palmyra, raising fears that the militants will destroy the historic site. (EPA)

Rami Abdel Rahman, the Observatory’s director, told The Independent 23 people were shot dead on Friday morning, including nine children.

“The children’s fathers were working in the Syrian government, not in intelligence or anything like that but as office workers,” Mr Rahmen said. “We heard that they were shot yesterday morning and we had it confirmed from people there in the evening.

“There was a lot of attention internationally on the situation yesterday; Isis probably wanted to change the focus onto them.”

The damaged Temple of Baal at Palmyra (Getty Images)

Palmyra, “an oasis in the Syrian desert”, lies north-east of Damascus and is known for its Roman-era architecture, described by Unesco as a marriage of Graeco-Roman techniques with local traditions and Persian influences. It was once a tourist hotspot before civil war broke out in Syria and contains a famous colonnaded main street and the temple of Baal.

Syrian troops are battling to repel Isis on the ground and are being supported by government war planes attacking their positions, according to the SOHR.

Western fighters join Kurds in battle against Isis Show all 9 1 /9 Western fighters join Kurds in battle against Isis Western fighters join Kurds in battle against Isis Foreign Fighters A 67-year old foreign fighter from Canada, nick-named by Kurdish fighters as Hewal Zinar, poses for a photo on April 19, 2015 Uygar Onder Simsek / AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 23-year old fighter and ex-US marine from the US, nick-named by Kurdish fighters as Hewal Agir, guards a look out point during clashes with Islamic State (IS) group fighters on April 17, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 26-year old from the US, nick-named by Kurdish fighters as Hewal Dilsad, shows a picture of his wife and son as he poses for a photo on April 14, 2015, in the outskirts of the north-western Syrian town of Tal Tamr Western fighters join Kurds in battle against Isis Foreign Fighters Ex-US marines aged 23 and 24 from the US, nick-named by Kurdish fighters as Hewal Agir (R) and Hewal Agit, guard a position during clashes with Islamic State (IS) group fighters on April 17, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A group of international foreign fighters pose for a photo on April 16, 2015, in the outskirts of the north-western Syrian town of Tal Tamr AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A foreign fighter poses for a photo with a machine gun on April 19, 2015, in the outskirts of Tal Tamr AFP Western fighters join Kurds in battle against Isis Foreign Fighters A 28-year old foreign fighter from the UK, nick-named by Kurdish fighters as Hewal Baran, poses for a photo on April 19, 2015, in the outskirts of the north-western Syrian town of Tal Tamr, north of Hasakeh AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A 21-year old from the UK and 23 year-old from the US nick-named by Kurdish fighters as Hewal Sores (L) and Hewal Agir guard a post on April 19, 2015 AFP/ Getty Images Western fighters join Kurds in battle against Isis Foreign Fighters A 67-year old man from Canada and a 40-year old from the UK, nick-named by Kurdish fighters as Hewal Zinar (L) and Hewal Cudi train on April 19, 2015, in the outskirts of the Tal Tamr AFP

Officials fear militants, who have already demolished two ancient archaeological sites in Iraq, will continue their devastating path of destruction in Palmyra. Isis has released videos of members bulldozing the 3,000-year old Assyrian archaeological site of Nimrud, in Iraq and demolishing ancient ruins in Hatra. The group has in the past justified the destruction of statues and figures by condemning them as idolatrous.