BEIRUT -- The office of Syria's president condemned on Monday the destruction of the 2,000- year-old iconic Arch of Triumph in Palmyra by the Islamic State group which controls the ancient city.

The rare statement of condemnation comes amid an intensive air campaign launched by Russia, which says it is helping the Syrian government combat the threat of the Islamic State group. The airstrikes, which started Wednesday, have spared the city of Palmyra but reportedly hit another area nearby controlled by the group in the central province of Homs.

Many of the airstrikes, often followed by government attacks, have largely targeted insurgents in the northwestern and central parts of Syria -- which are adjacent to strongholds of President Bashar Assad on the Mediterranean cost. The main IS strongholds are in the east.

The Islamic State group overran Palmyra in May, forcing government troops out. Since then, the group has destroyed two of its well-preserved ancient temples and other relics. The government's head of the Antiquities and Museums Department Maamoun Abdul-Karim called on Monday for taking back the city, "quickly."

Early Monday, activists and government officials said IS had destroyed the arch -- one of the most recognizable features of the city. It sits atop the colonnaded street that runs across Palmyra. The arch, built by Septimius Severus between 193 and 211 AD, was designed to minimize a 30-degree angle in the long colonnaded street and is topped by geometric and floral ornaments.

In a statement posted on its official Facebook page Monday, the presidency said the IS destroyed the arch "to avenge the light that disrupted their ignorance and darkness ... But it remains in the souls and minds of all Syrians and will remain."

The presidency described Palmyra, which in ancient times linked the Roman Empire to Persia and the East, as an integral part of the history of human civilization.

The city is a World Heritage site and the Director General of the U.N. cultural agency UNESCO, Irina Bokova, also condemned the arch's destruction -- calling it a new war crime that will not go unpunished.

"This new destruction shows how terrified by history and culture the extremists are, because understanding the past undermines and delegitimizes the pretexts they use to justify these crimes and exposes them as expressions of pure hatred and ignorance," Bokova said.

"Despite their relentless crimes, extremists will never be able to erase history, nor silence the memory of this site that embodies the unity and identity of the Syrian people."

Activists on a Facebook page from the city were despondent at the world reaction to Palmyra's destruction, warning that Assad should not be viewed as the city's saviour. The city has also come under intense government bombings in recent days, forcing thousands to flee.