China's ruling Communist party has ordered a survey of "unusual deaths" among officials, government websites showed Thursday, after reports that some had committed suicide to escape a crackdown on corruption.

An "urgent notice" called on officials to provide details of "party members who have died in unusual circumstances" since 2012, according to posts on government and party websites in three provinces seen by AFP.

China's President Xi Jinping has touted a crackdown on graft since assuming the party's top post in 2012, and some officials have reportedly killed themselves to escape possible criminal proceedings and prevent the seizure of their ill-gotten assets, to the benefit of their families.

Respected business news outlet Caixin said such notices had appeared on websites in at least nine provinces, adding that 50 party and government officials have been publically declared to have died of "unnatural causes" since 2012.

The Communist party is calling for a tally of deaths of officials at all levels, with details to be provided if the person was confirmed to have committed suicide, it added.

The survey requires suicides to be placed into several categories, one of which is "suspected of discipline violations", the party's standard euphemism for graft, it said.

The state-run China Daily said in September that Lou Xuequan, a former district Party chief in the eastern city of Nanjing, "reportedly hanged himself at his home" having been "dismissed from his position for accepting money as 'gifts'".

Xi's anti-corruption campaign has ensnared several current and former high-ranking officials, although most of the cadres investigated have been at low levels of government.

Critics say China has failed to implement institutional safeguards against graft such as public asset disclosure, an independent judiciary, and free media, leaving anti-corruption campaigns subject to the influence of politics.

Communist party academic Lin Zhe wrote in the China Daily last year that suicide has become a "judicial loophole for corrupt officials to escape punishment."

"Disciplinary and other investigations against a corrupt official... end in the event of their death," he wrote.

Officials who commit suicide "preserve their titles and honour, but also preserve the material gains they have made for their families, since their illegal income will no longer be confiscated," he added.