BEIRUT - Nearly 300 people have been killed in several days of fighting since the Islamic State group launched an attack against Syria’s ancient city of Palmyra, a monitor said Sunday.

The Britain-based Syrian Observatory for Human Rights, which relies on a network of sources on the ground, said the toll comprised 123 soldiers and loyalist militiamen, 115 IS fighters and 57 civilians. It said dozens of the civilians had been executed. The toll came as Syrian government forces Sunday pushed IS jihadists back from Palmyra, a UNESCO world heritage site, a day after the fighters had seized the northern part of the modern town.

But the Observatory said IS fighters were still one kilometre (less than a mile) from the archeological site and its adjacent museum which houses thousands of priceless artefacts. Fighting was still ongoing Sunday in the northern suburb of Palmyra and around Haql al-Hail gas field northeast of the city, the Observatory and IS said. IS seized Haql al-Hail on Saturday, the Observatory said, while the jihadist group posted pictures online of what it said was one of two checkpoints inside the gas field that it had overrun. Moreover, Islamic State militants have withdrawn from areas in the historic city of Palmyra they had seized on Saturday, a group monitoring the conflict in Syria and a Syrian official said.

The militant group’s attack on the government-held city of Palmyra, also known as Tadmur, has raised concern its World Heritage site could meet the same fate as ancient monuments the group has destroyed in Iraq. The Syrian Observatory for Human Rights, a UK-based monitoring organisation, said Islamic State fighters had pulled out of northern areas of the city taken on Saturday but still held a village to the north of Palmyra.

Maamoun Abdulkarim, the Syrian government’s antiquities chief, told Reuters the army had regained control of the whole city, and that the ancient ruins to the southwest of the city were unharmed. ‘The outskirts they had entered were all recovered,’ he said. Palmyra is strategically significant because it sits at a crossroads linking it to the cities of Homs and Damascus.

Islamic State has mounted frequent attacks on government-held areas in recent months, part of an apparent effort to expand beyond its strongholds in eastern and northern Syria. Syrian state TV, citing a military source, said the army had killed dozens of Islamic State militants to the east of Palmyra and were ‘pursuing their withdrawing remnants in several directions in the area’.