Older Chinese are angry and frustrated at the Communist Party of China's decision to increase the retirement age by at least five more years.

The party said it would "implement postponing the retirement age in a gradual manner" in an announcement reported by the official Xinhua News Agency. It gave no details or a reason.

The current retirement age is 60 for men. It is 55 for women civil servants and 50 for women workers. These have remained unchanged for four decades.

By 2038, however, the retirement age for both men and women will be 67, based on government plans.

The party proposes raising the age in the interim. While the party won't reveal the new retirement age, its latest five-year plan says China might consider gradually raising the age to 65 for men. This might mean an additional five years for both women civil servants and workers.

News of the higher retirement age sparked anger on China social media.

"Delaying retirement means we have to postpone our pension," one user on microblogging site Weibo said.

"Delaying retirement, which has no rationality or necessity, is out of ideological considerations that only when the interests and health of the people are sacrificed can there be economic development," wrote another elderly user.

China's latest attempt to raise the retirement age was described as unwise by an expert on China's social security.

Tang Jun, a researcher at the Institute of Sociology at the Chinese Academy of Social Sciences, warned the government to be careful. He said pushing through plans would lead to "worrying consequences."

Instead, Tang suggested employers and employees be allowed to negotiate retirement ages.

"The worst plan is to postpone retirement," he said.

A similar plan in 2013 failed in the face of public opposition.

In 2018, 250 million of China's 1.4 billion people were 60 years or older. This represents 18% of the population. This percentage will likely jump to 21% in 2035, 25% in 2046 and 33% by 2053 - even as the population declines owing to a low birth rate.

This means over the next 30 years China's older population will increase by 193 million. On the other hand, its working-age population will fall by 176 million owing to a fertility rate that is one of the world's lowest.

These factors will put pressure on China's already pressured pension system and potentially cause a fund crisis.