A data set of nearly eight million articles about Ukraine collected from more than 8,000 Russian websites since 2014 shows that references to Nazism were relatively flat for eight years and then spiked to unprecedented levels on Feb. 24, the day Russia invaded Ukraine. They have remained high ever since.

The data, provided by Semantic Visions, a defense analytics company, includes major Russian state media outlets in addition to thousands of smaller Russian websites and blogs. It gives a view of Russia’s attempts to justify its attack on Ukraine and maintain domestic support for the ongoing war by falsely portraying Ukraine as being overrun by far-right extremists.

News stories have falsely claimed that Ukrainian Nazis are using noncombatants as human shields, killing Ukrainian civilians and planning a genocide of Russians.

The strategy was most likely intended to justify what the Kremlin hoped would be a quick ouster of the Ukrainian government, said Larissa Doroshenko, a researcher at Northeastern University who studies disinformation. “It would help to explain why they’re establishing this new country in a sense,” Dr. Doroshenko said. “Because the previous government were Nazis, therefore they had to be replaced.”