A Communist official has issued a "high-profile warning" about ideological problems at China's top think-tank, domestic media said Monday, as the party leadership exerts its authority over state-run institutions.

Experts at the state-affiliated Chinese Academy of Social Sciences (CASS) are spreading false ideas online and allowing foreign "infiltration" in its work, warned Zhang Yingwei, a senior anti-corruption official with the ruling Communist Party, the Global Times reported.

Zhang also accused the think-tank -- which makes policy recommendations to the government -- of using academic research as a disguise for other purposes and fabricating false theories using the Internet, the newspaper reported.

He urged staff at CASS to "remain highly alert to political sensitive issues with no one making exceptions", and to "strengthen ideology construction", it said.

The warnings come as overseas critics say China's already-limited academic freedom is in peril.

At the end of last year, Peking University professor Xia Yeliang -- one of the original signatories of Charter 08, a daring petition urging greater protection of human rights and democratic reforms in China -- lost his post.

The Global Times linked Zhang's warning to "sweeping anti-graft campaigns targeting government officials and state-owned enterprises" launched by the party leadership that took power under Xi Jinping in late 2012.

The campaign -- which has been widely touted by President Xi -- has netted a number of high- and low-ranking officials, but in the absence of systemic reforms analysts say it serves more to exert political control than to eliminate corruption.

Since taking charge, Xi has also presided over the arrests of dozens of rights activists, as well as a crackdown on popular bloggers and the spread of "rumours" through social media.

Social media sites such as the Twitter-like microblog Sina Weibo have become a popular alternative source of information to the tightly censored, state-controlled media.

CASS conducts research on politics, economics, history and other fields.