Mongolia on Monday called for more support from Russia, Britain, and other countries to repatriate hundreds of cultural artefacts, some dating back over two millennia.

Key artefacts include a letter from Mongolia’s first prime minister declaring independence from China’s Manchu dynasty, currently held at the British Library in London, the Mongolian government said in a statement.

Artefacts associated with the Persian statesman Rashid al-Din who worked in the courts of several Mongol rulers of Persia in the 13th and 14th centuries are being kept at the Museum of Edinburgh, it also said.

In recent decades, many countries, including former colonies of European empires, have requested the return of cultural and historical artefacts taken away years ago, many of which are housed in museums reluctant to surrender their collections.

Mongolia has made some headway in claiming back its cultural artefacts. Earlier this year, the United States returned dinosaur fossils taken out of Mongolia, including the skull of an alioramus, a smaller version of a tyrannosaurus rex that lived 70 million years ago.

At a forum in Russia last week, Mongolia’s Culture Minister Ch.Nomin also requested Moscow’s help with identifying and returning artefacts that were sent to Russia for research and restoration purposes one hundred years ago, including artefacts from the Hunnu dynasty 2,000 years ago excavated from the Noyon Uul burial site by Russian explorer Pyotr Kozlov in the 1920s.