Several US cities under New Year terror threat. Is your city on the list?

At least four cities have massively increased security ahead of New Year's celebrations.

A cocktail of circumstances has the FBI concerned that a terrorist attack is all but inevitable on New Year's. A maximum effort is underway combining heavy policing, rapid investigation, and possible arrests, across the United States. Officials in New York, Washington, and Los Angeles are particularly concerned following a terror briefing for officials in those cities. Las Vegas has a notable National Guard presence, but was not listed by federal officials.

LOS ANGELES, CA (California Network) - Yesterday, Russia launched over 100 airstrikes and claims to have hit several top ISIS leaders outside Raqqa, the de facto capital of the Islamic State. Typically, ISIS orders terrorist attacks within days of losing a key figure or leader. The Paris terror attacks happened the day after Jihadi John was killed.

Federal officials have cited an uncorroborated threat against New York, Washington, and Los Angeles. In response several cities have stepped up security. In New York, ahead of the New Year's celebrations, about 6,000 police have been dispatched, more than ever before in the city's history.

In Las Vegas, there are reports that the National Guard is out. These troops are supposedly participating in a military exercise, "Vigilant Sentinel."

Authorities in Los Angeles are also taking unspecified steps to ensure events like the Rose Parade and the widely attended Rose Bowl are safe for the public.

Some analysts believe 2016 will be a major year for terrorist attacks as ISIS faces more pressure to demonstrate that Allied and Russian attacks have strengthened the caliphate rather than weakened it.

US authorities warn that all citizens should be vigilant as they enjoy their New Year's celebrations, particularly in large urban areas. They note there are no specific threats which mention specific plots, but they are not taking any chances.