A New York Police Department (NYPD) officer stands in a corridor, at the New York Port Authority subway station, in New York City, Dec. 12, 2017. Photo: Reuters / Brendan McDermid.

Arrests and plots linked to domestic Islamist extremism in the US increased by 50 percent last year, new data published by the Anti-Defamation League (ADL) on Monday showed.

According to the data, compiled by the ADL’s Center on Extremism, there were a total of 30 arrests linked to domestic Islamist extremism in 2019, nine of which were for terror plots.

“While there were no attacks or murders linked to domestic Islamist extremism last year, the findings indicate that Islamist extremism still poses a significant threat to the United States,” an ADL statement said.

ADL CEO Jonathan Greenblatt commented, “Make no mistake — the threat of Islamist extremist activity in the United States is serious and cannot be ignored. We are deeply grateful for the efforts of federal and local law enforcement to investigate and disrupt these potentially dangerous attacks.”

The ADL statement added, “In addition to the nine individuals arrested for plotting attacks, 21 others were arrested for engaging in domestic criminal activity motivated by Islamist extremism. Of those 21 individuals, a large majority faced charges for attempting to provide material support to ISIS. Approximately 70 percent of domestic Islamist extremist criminal activity in 2019 was inspired by ISIS, which has reportedly lost all of its territory in Iraq and Syria.”

Oren Segal — vice president for ADL’s Center on Extremism — noted, “ISIS’s ability to continue inspiring a large percentage of violent activity even after being effectively disbanded demonstrates the lasting influence of its violent ideology and propaganda on Islamist extremist activity in the United States. As long as the ideology persists and spreads online, extremists will continue to be inspired by violent rhetoric and instruction.”