Islamic State fighters tightened their grip on the historic city of Palmyra in Syria, days after capturing a provincial capital in neighbouring Iraq, suggesting the growing momentum of the group which a monitor says now holds half of Syrian territory.

The twin successes pile pressure not just on Damascus and Baghdad, but also throw doubt on US strategy to rely almost exclusively on air strikes to defeat Islamic State.

Islamic State said in a statement posted by followers on Twitter yesterday it was in full charge of Palmyra, including its military bases, marking the first time it had taken a city directly from the Syrian military and allied forces.

Around a third of the 200,000 people living in Palmyra may have fled in the past few days during fighting between government forces and Islamic State militants, the UN human rights office said on yesterday.

Human, civilised society has lost the battle against barbarism

Citing what she said were credible sources, UN human rights spokeswoman Ravina Shamdasani in Geneva also said there were reports of government forces preventing civilians leaving until they themselves fled and Islamic State, also known as Isil, took control of the city.

“Isil has reportedly been carrying out door-to-door searches in the city, looking for people affiliated with the government. At least 14 civilians are reported to have been executed by Isil in Palmyra this week,” Shamdasani said.

The Britain-based Syrian Observatory for Human Rights said the al-Qaeda offshoot now controls more than half of Syrian territory following more than four years of conflict which grew out of an uprising against President Bashar al-Assad.

The ultra hardline group has destroyed antiquities and monuments in Iraq and there are fears it might now devastate Palmyra, home to renowned Roman-era ruins including well-preserved temples, colonnades and a theatre.

The UN cultural agency Unesco describes the site as a historical crossroads between the Roman Empire, India, China and ancient Persia and a testament to the world’s diverse heritage.

“We may have different beliefs ... different views, but we have to protect such incredible vestiges of human history,” Unesco Director General Irina Bokova told Reuters TV.

“This is the fall of a civilisation,” Syria’s antiquities chief Maamoun Abdulkarim said.

“Human, civilised society has lost the battle against barbarism.”

Al-Azhar, the centre of Islamic learning in Egypt, called on the world to protect Palmyra, saying the destruction or looting of cultural heritage was religiously forbidden.

The assault on the city is part of a westward advance by Islamic State.

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