Universities and colleges in China should bar “textbooks promoting western values” from classrooms to ensure that students are not influenced by “negative ideas,” China's education minister Yuan Guiren said on Thursday, according to a report by Xinhua news agency.

In the latest sign of tightening restrictions on academics in China in recent months, Yuan reportedly said that not only should authorities tighten control over imported textbooks, they should also ensure that remarks that disparage the ruling Communist Party of China (CPC), the country’s constitution or the ideology of socialism should never be made in classrooms.

Teachers should not be allowed to “vent their personal grudges” and should provide “positive guidance” to the students, Xinhua quoted Yuan as saying during an educational symposium attended by representatives from leading Chinese universities.

“Teachers must stand firm and hold the ‘political, legal and moral bottom line,'" Yuan reportedly added.

State control over educational institutes in China has intensified since President Xi Jinping assumed the Party’s leadership in 2012. In recent months, several outspoken academics, perceived as being critical of the government, have been either sacked or imprisoned.

In October last year, Chinese economist Xia Yeliang, a professor at Peking University, was dismissed after he called for democratic reforms in the country. Earlier, in September, prominent Uighur scholar Ilham Tohti -- who had urged greater dialogue between Beijing and the Uighur minority in the restive Xinjiang region -- was imprisoned for life for advocating separatism. Several of his students were also jailed.

Yuan’s comments are in line with previous statements made by the Chinese leadership.

In December last year, Xi urged universities to provide “ideological guidance” to students and transform themselves into “socialist universities with Chinese characteristics,” according to media reports. Earlier this month, the CPC had, in a directive, called on universities to ensure that theories of Chinese socialism and Marxism “get into the students’ heads” and do not remain restricted to textbooks and classrooms.