Masked men in dark clothing stopped a jewelry merchant's car, beat him and stole $2 million worth of diamonds during a brazen Los Angeles street heist, police said Friday.

The merchant appears to have been targeted by professional thieves, police Lt. Alan Hamilton said. No arrests have been made.

"This isn't unusual," Hamilton said, noting there are large jewelry thefts each week in Southern California. "It's usually South American nationals who are very organized and professional."

The victim told investigators he was driving down a well-lighted North Hollywood street about 10:10 p.m. Thursday when his car was blocked by two vehicles. and five to six men jumped out.

The men ran up to the merchant's car and smashed a window while struggling for the backpack containing the diamonds. The attackers got back in their vehicles and fled.

The victim followed the thieves but lost them in traffic.

The victim, who was treated and released from a hospital with minor injuries, was described as a merchant in the jewelry trade business. His name was not released.

"We are treating it as a legitimate crime," the lieutenant said.