But most European operators said Friday they were satisfied with precautions already in place.
In New York, Philip Smith, president of the Shubert Organization, which owns more than a dozen Broadway theaters, said security "has been stepped up in recent days," but he declined to discuss specifics. Smith added that the company already has its own security force and "we do liaison with the police department."
Arnold Crook, chairman and chief executive of two of London's most elegant theaters - the Theatre Royal Haymarket and the Strand - said Friday that he was hiring more guards and requiring bag checks at the door.
Both venues are housing hit shows: The Haymarket has David Hare's "The Breath of Life," starring Judi Dench and Maggie Smith, while Brenda Blethyn is at the Strand in George Bernard Shaw's "Mrs. Warren's Profession."
Other London operators were more relaxed.
"We always ask staff to be alert," said Nicholas Allott, managing director of Cameron Mackintosh Ltd., which owns seven theaters and manages two others in the West End.
In Berlin, no extra security measures were reported.
"In Germany, we have no comparable situation to the war in Chechnya," said Stefan Adam of the Deutsche Staatsoper. "Security authorities have given us no notification of any increased danger, and therefore we have not reacted to the Moscow hostage drama by increasing security."
Officials at Paris' two opera houses - the ornate, 19th century Palais Garnier and the ultramodern Opera Bastille - said they started searching bags after the Sept. 11 attacks in the United States and weren't ordering additional precautions.
La Scala opera house in Milan, Italy, and several theaters in Rome likewise reported no changes in security measures.
Andre Ptaszynski, chief executive at Andrew Lloyd Webber's Really Useful Theaters, which oversees 14 London theaters, said a threat like the Moscow siege was considered "a low-risk scenario" in London.
Ptaszynski noted that violence by the Irish Republican Army rarely affected theaters in London.
"We still have a peace accord in Northern Ireland," he said, "and no IRA activity on the mainland, so it's hard to see this sort of thing being a problem...."
At the Royal Opera House, spokesman Christopher Millard said, "We already have quite a visible security presence - in the nicest possible way."
Though he is tightening security at the Haymarket and the Strand, Crook said it was important not to scare audiences away from London's theater district.
"It's just not possible to have guards standing in attendance with rifles," said Crook. "It's hard enough to get people to the West End as it is."
By Matt Wolf