Five men have been arrested in Croatia for allegedly stealing €2m (£1.7m) worth of jewellery owned by a member of Qatar’s royal family from Venice’s Doge’s Palace in early January.

In a case that baffled police, the thieves managed to deactivate the alarm system, break into a reinforced case, seizing some earrings and a brooch before blending into the crowds during the final day of the four-month Treasures of the Mughals and the Maharajahs exhibition, which brought together a collection of five centuries of Indian craftmanship.

Local police called on experts to help try to establish how they managed to pull off the heist in the Chamber of the Scrutinio, one of the rooms within the vast premises of the palace, which was once the residence of the former republic of Venice’s rulers and now attracts up to 4,000 visitors a day.

Four Croatians and one Serbian, aged between 43 and 60, were arrested in the Croatian capital, Zagreb. One of the suspects was said to be part of the Pink Panthers, an international network of jewel thieves. Investigators had been on the hunt for the same suspect following the robbery of €10m worth of jewels during an exhibition in Basel, Switzerland in 2011.

The mayor of Venice, Luigi Brugnaro,said that justice had been delivered “to those who thought they could commit a crime in Venice and get away with it”.

“On behalf of the city of Venice and me personally, I would like to express my heartfelt thanks to the public prosecutor, Venice police and all the police forces involved in arresting the five leaders of the theft,” he said in a statement.

“Since the theft, Venice and the city’s museums foundation have ensured maximum cooperation with investigators. These past months of careful intelligence work, during which I was constantly informed of developments, were even more complex due to the collaboration of police officers from different nations, but we were able to first identify the guilty and then arrest them.”

Alessandro Bertasi, a spokesperson for the mayor, said the jewels had not yet been retrieved but that investigations were ongoing.

The collection comprises 270 pieces of Indian-inspired jewellery and precious stones spanning 400 years from the Mughal period to the present.