Thieves have stolen millions of pounds worth of Indian jewels in broad daylight from an exhibition at a Venetian palace.

A brooch and a pair of earrings were taken from the famed Al Thani Collection at the Doge’s Palace in Venice on Wednesday, police said.

The audacious heist occurred on the final day of a four-month exhibition featuring 270 items showcasing treasures from the time of the Mughal Empire.

Venice police said one thief kept watch while another opened a display case and grabbed the jewellery. They were somehow able to delay the security alarm, which went off at 10am, for long enough to make their escape.

Police immediately sealed the area, but the thieves blended in with the crowds and got away.

Vito Gagliardi, chief police commissioner, said: "We are clearly dealing here with two skilled professionals who managed to pull off their feat despite all the display rooms being fitted with technologically highly sophisticated (alarm) systems."

The stolen jewels were made of gold, platinum and diamonds, police said, and news reports estimated their value in the millions of euros.

The palace, known as the Palazzo Ducale, is now a museum and one of Venice's top tourist destinations.

The Al Thani Collection is a renowned collection of 270 pieces of Indian and Indian-inspired jewellery and precious stones, spanning 400 years from the Mughal period to the present and assembled by Qatar's Sheikh Hamad bin Abdullah Al Thani.

Forbes magazine said "there is no comparable collection on the planet”.

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The "Treasures of the Mughals and the Maharajas” exhibit closed on Wednesday. It was the latest stop in a travelling exhibit that has brought the collection to Paris' Grand Palais, London's Victoria and Albert Museum, New York's Metropolitan and the Miho Museum near Kyoto, Japan.

A spokesman for the collection, John Maxse, said it was in contact with Italian authorities and Venice's Foundation of Civic Museums, which runs the Doge's Palace.

In a statement, the foundation said the brooch and earrings stolen were "contemporary pieces and consequently are of less historical value than other items in the collection."

Venice police said the items are so unique they will be nearly impossible to sell on the market.