President Xi Jinping's wide-ranging reform push, covering everything from politics to the military, has come up against "unimaginably" fierce resistance, according to a tersely worded commentary carried by state media on Thursday.

In unusually strong language, the article said the reforms were at a critical stage and had encountered immense difficulties, affecting the interests of various groups.

"The in-depth reform touches the basic issue of reconfiguring the lifeblood of this enormous economy and is aimed at making it healthier," the article said. "The scale of the resistance is beyond what could have been imagined."

The commentary was attributed to "Guoping", an apparent pen name used by state media to comment on major state and Communist Party issues. It appeared in state media including the websites of CCTV and Guangming Daily.

Observers said the commentary suggested the reforms had not achieved the desired results and were opposed by various factions.

Xu Yaotong, a political science professor at the Chinese Academy of Governance, said the publication came amid concerns the anti-corruption campaign, which had targeted several top military officials and politicians, was waning and that other reforms had attracted opposition.

"The tone [of the commentary] reads furious," Xu said.

"I feel that the central leadership has started to worry, based on the message indicated in the Guoping article."

He said the resistance could be from any of three powerful groups: retired leaders who wanted to exert influence, cadres whose power had been weakened and civil servants unhappy with austerity rules.

The publication comes after a series of People's Daily articles this month criticizing retired cadres for continuing to exert influence behind the scenes. It also follows the end of the annual agenda-setting gathering of the party elite in the Hebei seaside resort of Beidaihe.

Beijing-based political commentator Zhang Lifan said the commentary signaled that "things are not going well".

"Obviously they did not reach any consensus at the political activities in Beidaihe. Different groups are pursuing their own ways," he said. "This is a test of the leadership's ability to execute its mission."

Zhang said the goal of having the market play a decisive role in the "allocation of resources" was one case of a target that was still a long way off.

"The reform has to address politics and the economy at the same time. If the political system does not change, then inertia in the bureaucracy will just send the reform around in circles," he said.

Renmin University political science professor Zhang Ming said the reform push had not only failed to deliver results, it might have gone backwards.

"There's resistance not just to the reforms, there's other resistance too," he said.