​An extraordinary scene unfolded in the ancient city of Palmyra tonight.

The famous Russian Mariinsky Theatre Orchestra from St. Petersburg played a concert in the city's Roman theatre — only six weeks after ISIS was forced out of the historic Syrian site.

The assault on Palmyra started in early March, with Russian airstrikes followed up by Syrian ground troops who moved in to oust ISIS, ending the militant group's 10-month reign of terror over a town whose famed 2,000-year-old ruins once drew tens of thousands of visitors each year.

Much of the Roman theatre, a UNESCO world heritage site, remains undamaged, but parts of it were blown up by ISIS militants.

Dusk falls in Palmyra a Unesco World Heritage site. The Russian and Syrian armies are protecting the ruins and de-mining the area, after battling ISIS In March. (Susan Ormiston/CBC)

Ambassadors from UNESCO, the United Nations' Educational, Scientific and Cultural Organization, have unanimously adopted a Russian motion to restore the historic parts of Palmyra that were damaged under ISIS occupation.

Cellist Sergei Roldugin performed at the theatre, which ISIS used as a venue to conduct public executions during its occupation of Palmyra. Roldugin, a close friend of Russian President Vladimir Putin, was named in the Panama Papers.

Conducting the orchestra was Valery Gergiev, also a supporter of Putin's.

Syrian army soldiers stand on the ruins of the Temple of Bel in the historic city of Palmyra on April 1. Many of the city's heritage sites were destroyed under ISIS occupation. (Omar Sanadiki/Reuters)

In opening remarks, Gergiev said that with the concert, "We protest against the barbarians who destroyed monuments of world culture."

There was also a video link-up in which Putin addressed the audience, saying he regarded the concert "as a sign of gratitude, remembrance and hope."

Valery Gergiev is a famous Russian conductor and supporter of President Vladimir Putin. (Helen Atkinson/Reuters)

Thursday's concert has echoes of a similar performance, also conducted by Gergiev, in August 2008, when the Mariinsky played in front of the bombed-out parliament of the self-proclaimed Republic of South Ossetia after Russian forces defeated the Georgian army in a short war over the territory.