T he Federal Bureau of Investigation and the Department of Homeland Security have indicated that lone wolf attacks are the greatest threats to this year's July 4 celebrations in New York City and San Francisco.

Attacks perpetrated by lone actors are the biggest terrorism threat to July 4th festivities in New York City and elsewhere, federal authorities said in a threat assessment obtained by CNN.

Former Secret Service agent discusses enhanced security protocols for Fourth of July celebrations across the country amid escalating tensions with Iran after US military strikes.

As cities across America prepare for massive July 4 gatherings, federal authorities have sounded the alarm over potential security threats from lone-wolf attackers and unauthorised drone activity.

In a joint bulletin, the FBI, Department of Homeland Security and other law enforcement agencies said individuals or small groups motivated by political, racial or personal grievances are most likely to target large gatherings like the Macy’s fireworks show in New York City, or other celebrations across the country.

Intelligence bulletins sent out ahead of the holiday warn of copycat attacks and homegrown extremists targeting July 4 celebrations in City and San Francisco.

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