Nine pieces of historic Chinese porcelain worth around a million euros ($1.1 million) were stolen from a museum in Cologne overnight, authorities in the German city said Wednesday.

"Unknown persons" managed to break into the Museum of East Asian Art through a window and steal the pieces from display cases, according to police.

Nine items taken date from the 16th to the 19th century, city authorities said in a statement.

The pieces include two vases and a bowl from the Ming period and several items dating back to the Qing dynasty.

Some of were part of the museum's founding collection.

Since the stolen items are well documented and easily identifiable, museum director Shao-Lan Hertel said she was hopeful they will eventually find their way back.

Stefan Charles, the city councillor for arts and culture, announced a review of the museum's security.

The theft comes after five gang members were jailed in May for snatching priceless 18th-century jewels from a museum in Dresden.

In what German media dubbed the biggest art heist in modern history, the thieves made off with a haul worth more than 113 million euros ($123 million) from the Green Vault museum in 2019.

The loot included a sword with a diamond-encrusted hilt and a shoulder piece which contained a 49-carat Dresden white diamond.

Some, but not all, of those items were recovered

In another heist, burglars made away with a stash of Celtic coins worth several million euros from a museum in southern Germany's Manching city last November.