WASHINGTON - The U.S. violent crime rate fell for the second year in a row in 2018, largely extending a decades-long decline, the FBI said in its annual crime report released on Monday.

There were an estimated 369 violent crimes per 100,000 residents in 2018, a decrease of 3.9 percent from the 2017 level. In 2017 also violent crime fell though at a lower rate.

The back-to-back declines follow an increase of 8% in 2015 and 2016 and put the violent crime rate nearly 15 percent lower than a decade ago and more than 50 percent below the levels seen in the early 1990s when the U.S. was engulfed by a wave of crime.

The report comes just weeks after the Justice Department's statistics arm released a survey showing an increase of 22 percent in the number of violent crime victims in the United States over the past three years.

The annual household survey includes both crimes reported and not reported to police, whereas the FBI's closely watched stats are based on voluntary reporting by thousands of police departments around the country.

The rise and then fall of violent crime in recent years has fueled a debate among policy makers and criminologists over their underlying causes and whether they signal a new trend.

Coming into office, the Trump administration blamed the 2015-2016 surge in violent crime on the former President Barack Obama's immigration policies and then took credit for its more recent turnaround by instituting tough on crime, pro-law enforcement policies. But that's a simplistic reading of the long-term trend, according to criminologists.

What's clear is that violent crime remains substantially lower the 1990s peak despite the recent fluctuations and stubornly high rates in some major cities.

“Across all three metrics (murder, violent crime and overall crime), crime in the United States remains at or near the bottom of downtrend that has lasted more than a quarter century,” Ames Grawert, a criminologist at the Brennan Center for Justice at New York University wrote in a report.

But not all U.S. cities have equally shared in the decline, he said, adding that more “innovative solutions are needed to preserve and expand on public safety gains."

The overall drop in violent crime was seen across most categories of crime.

The murder rate also fell for the second consecutive year, decreasing by 6 percent to nearly 5 murders per 100,000 people. Though a tad higher than a recent low in 2014, the overall U.S. murder rate remains nearly half the 1991 high of almost 10 murders per 100,000 residents.

Large cities saw a marked decline in murder. In cities with a population of more than 1 million people such as Chicago, the overall murder rate fell by 8.5 percent.

In Chicago, it tumbled by 14 percent to 21 murders per 100,000 residents. In Baltimore, another city that has experienced high murder rates in recent years, it fell by 9 percent to 51 murders.

The decades-long decline in violent crime has been most pronounced in New York City, the nation's largest city. Once known as the murder capital of the United States, the city recorded 287 murders in 2018, five fewer than 2017 and down 87 percent from a record 2,245 murders in 1990.

Among other categories of violent crime, robbery saw the largest decline, decreasing by 12 percent to 86.2 robberies per 100,000 people. The rate of rape crimes, however, rose by 2.1 percent, likely due to an increase in reporting, to 42.6 rapes per 100,000 residents.