A competing bid from a group including CEO Denis Ladegaillerie violates rules around tender offers, the board says.
The four men charged with carrying out the deadly strike showed signs of being severely beaten while appearing in court on Sunday.
"The whole country, our whole people, mourns with you," Russian President Vladimir Putin said.
The Grammy-winning musician performed frequently at La Scala opera house in Milan.
Putin said authorities detained a total of 11 people, including four suspected gunmen who attacked concertgoers.
The strike occurred as crowds gathered at a concert for Russian rock band Picnic.
This week's most important music industry stories in Canada.
The company's 106.7 million paying subscribers contributed to a 39% jump in music subscriptions revenue.
After years of trying to protect physical sales, local record companies are increasingly embracing digital formats with streaming's growth.
COO Francesca Bodie-Leiweke discusses the company's international strategy as it prepares to open Coop Live in Manchester.
