One of China's top universities has urged students and teachers to "fight against" criticism of the ruling Communist Party, an influential party journal said, in the latest curbs on free expression.

The move by Peking University, which at one time was a bastion of free speech in China, underscores increasing anxiety of criticism among party leaders and is a sign of President Xi Jinping's politically conservative agenda.

Curricula and speech at Chinese universities are tightly controlled by the government, though students at Peking University have at times pushed the limits, including during the 1989 Tiananmen Square pro-democracy protests that were brutally suppressed by the army.