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.

Special events with high attendance and media coverage remain attractive targets for lone offenders and violent extremists seeking to cause mass casualties or draw attention to their causes.

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.