Don Emmert / AFP / Getty Images file A 1729 Stradivarius known as the Solomon, Ex-Lambert

A 300-year-old Stradivarius worth millions of dollars was stolen from a concert violinist by thieves who shot the musician with an electric stun gun just after he had performed with the instrument in suburban Milwaukee, police said on Tuesday.

"It appears the violin was the primary target of this robbery," Milwaukee Police Chief Edward Flynn told reporters, adding that the two thieves were seen fleeing the scene of the crime in a minivan.

The so-called Lipinski Stradivarius, an instrument made in 1715 and distinguished by unique striations on its back, was stolen on Monday night at a college campus in Wauwatosa, immediately west of Milwaukee, Flynn said.

The instrument was on loan to violinist Frank Almond of the Milwaukee Symphony Orchestra when it was taken from him following a performance, Flyn said.

Police said Almond was subdued with a stun gun fired at him by one of the thieves, who then jumped into the waiting getaway vehicle driven by another suspect.

Violins such as the one stolen can sell for $5 million to $10 million, Flynn said. He added that the FBI has entered the Lipinski into its international art theft database.

"This violin is very valuable, but very valuable to a very small population," Flynn said in a news conference carried by ABC affiliate WISN on its website. "This is not something that can be easily sold for even a fraction of its monetary value."

Milwaukee Orchestra president Mark Niehaus said rare instruments such as the stolen Stradivarius are in circulation because they "need to be played to live on."

The missing instrument is one of roughly 600 violins, violas and cellos built by the famed Italian maker Antonio Stradivari that are still in existence.

Korean-born classical musician Min-Jin Kym's 300-year-old Stradivarius violin was snatched in November 2010 when she stopped at a London restaurant to buy a sandwich. That instrument was found three years later and sold at auction for $2.3 million in December, according to the BBC.

A rare Stradivarius violin that once belonged to the granddaughter of English poet Lord Byron sold for $15.9 million in 2011 at a charity auction for Japanese disaster relief.