Major US theme parks in Florida and California, including Disney, SeaWorld and Universal Studios, are adding security measures to screen visitors.
Walt Disney Co is also ending sales of toy guns at its parks, banning visitors over the age of 14 from wearing costumes and adding randomised secondary screenings of visitors with metal detectors.
Guests at Disney theme parks in Anaheim, California, and Orlando, Florida, previously had their bags checked by hand and with a handheld metal detector, officials said on Thursday.
The moves follow a December 2 shooting rampage that killed 14 people in San Bernardino, California, by a married couple inspired by Islamic State, and the November 13 attacks in Paris in which 130 people died.
The theme park companies did not refer to either event in announcing the increased security, although Disney did say it was increasing security in light of recent events. Anaheim is about 80km southwest of San Bernardino.
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SeaWorld Entertainment Inc is also using metal detectors at its Orlando park, according to local media reports.
Universal is testing the use of metal detectors at its Orlando and Hollywood parks, but not in response to a specific incident, spokesman Tom Schroder said.
"We just want our guests to feel safe," Schroder said.
At Disney's Florida parks, more uniformed law enforcement officers will be patrolling the parks, and less visible security measures are being enhanced, the company said.
"We continually review our comprehensive approach to security and are implementing additional security measures, as appropriate," Disney said in a statement.
A man was arrested last weekend after trying to bring a gun into Disney's Magic Kingdom park at Walt Disney World, the Orlando Sentinel newspaper reported.
