BEIJING — At least a dozen young activists who took part in a national campaign for workers’ rights in China are missing, friends said on Sunday, in what appeared to be an effort by the government to silence one of the most visible student protests in years.

Unidentified men in at least five Chinese cities rounded up the activists, who are recent graduates of elite universities, over the past few days, according to friends of the activists. The men beat several activists before pushing them into cars and driving away, the friends said.

The activists, describing themselves as ardent communists who fervently believe in the ideals of Marx and Mao, have waged an unusual campaign against inequality and corporate greed that has gained traction at some of China’s top schools.

The campaign has put the ruling Communist Party, which prides itself as a socialist guardian of workers’ rights, in an awkward position. Now, in line with President Xi Jinping’s efforts to curtail dissent and political organizing, the party appears to be redoubling efforts to quash the movement.