White nationalists and self-identified Nazi sympathizers located mostly in the United States use Twitter with "relative impunity" and often have far more followers than militant Islamists, a study being released on Thursday found.

Eighteen prominent white nationalist accounts examined in the study, including the American Nazi Party, have seen a sharp increase in Twitter followers to a total of more than 25,000, up from about 3,500 in 2012, according to the study by George Washington University's Program on Extremism that was seen by Reuters.

The study's findings contrast with declining influence on Twitter Inc.'s service for Islamic State, also known as ISIS, amid crackdowns that have targeted the militant group, according to earlier research by report author J.M. Berger and the findings of other counterextremism experts and government officials.