One of China's longest-running and largest independent film festivals has suspended operations "indefinitely", with the organisers saying it was now "impossible" to organise a festival with a "purely independent spirit".

The China Independent Film Festival (CIFF), which was established in the eastern city of Nanjing in 2003 and has held 14 sessions so far, made the announcement late on Thursday.

It did not provide more details of what pushed it to such a decision, but the move comes amid growing media censorship in China, which has seen regulators crack down on content they believe to violate "socialist core values".

"We believe, that under current local organisational conditions, that it is impossible to organise a film festival that truly has a purely independent spirit and which is effective," the CIFF said on its official WeChat account.

"Of course, to those grassroots film festivals that under the mask of security still try to encourage independence, we express our respect."

CIFF showed around 1,000 films and documentaries since its founding, according to the South China Morning Post (SCMP) newspaper. A number of them touched on topics considered sensitive in China, such as homosexuality and the relocation of residents under the Three Gorges dam project.

Zhang Xianmin, a professor from Beijing Film Academy who has been the CIFF's core organiser, told the SCMP on Friday that the closure was "normal".

"We are just back to the usual rule under the Party. We just went back to 20 years ago, when there was no room and opportunity for independent films."

"If we had promoted the commercialisation of CIFF, that might have made it safer and we could have had the chance to survive."