Months of civil unrest have coincided with a significant rise in social media posts critical of police that sometimes are laced with violent themes, including calls to destroy property and attack officers, according to research released Monday morning.

The report, by the Network Contagion Research Institute (NCRI), which previously has studied right-wing violence from groups such as the “boogaloo boys,” warns that some left-wing groups have embraced similar social media tactics, including memes and humorous catchphrases, to spread their messages and possibly help coordinate offline activity. The researchers pointed to possible signs of such coordination associated with riots in Seattle, Portland and other cities on July 25, involving fires, looting and property damage…

Some memes that spread on social media depict police officers being shot or their vehicles burned. One post from a left-wing group cited by the report called for the use of laser pointers to obstruct surveillance and the lighting of fires at police barricades. Another post urged people to use 3-D printers to make guns that can’t be traced by authorities.

Comments using anti-police slogans surged nearly 300 percent on Reddit and more than 1,000 percent on Twitter during the unrest triggered by the killing of George Floyd in May, according to the report. It also described the growth of left-wing networks on Facebook, with such groups as Redneck Revolt and the Socialist Rifle Association boasting about 50,000 and 40,000 members, respectively — numbers that still pale in comparison to right-wing communities online.