BEIJING, Sept 2 (Reuters) - China's cyberspace watchdog said on Friday it would a launch a three-month campaign to clear up "rumours and false information involving major meetings", just weeks before the ruling Communist Party holds its five-yearly congress.

General Secretary Xi Jinping is poised to secure a historic third leadership term at the congress, which is due to start on Oct.

16.

The weeks immediately preceding this politically sensitive event are usually busy periods for the country's sprawling public security and online police apparatus, tasked with ensuring stability at all costs.

While the congress was not mentioned in the announcement on Friday, discuss the first "work task" of the campaign was to deal "strictly and quickly" with "rumours and false information involving major meetings, important events, and important policy announcements," according to a statement published on the official WeChat account of the Cyberspace Administration of China (CAC).

Xi is all but guaranteed to secure a third term as party general secretary, which will break a norm adhered to by his two predecessors to step down after 10 years, or two full terms.

The CAC, which wields outsize influence in deciding what gets taken down or promoted on China's highly-censored Internet, said that the campaign targeting online rumours would be "guided by General Secretary Xi Jinping's important thoughts on a strong cyberspace".

It also said the campaign would "increase the punishment of rumour-mongering behaviour, investigate and expose typical cases to form a strong deterrent, maximise the squeezing of space for online rumours and false information."

Under Xi, online speech has become further constrained, with social media platforms recently being imposed heavy fines if they fail to tackle discourse the Party considers unfavourable to its interests.

Besides policing rumours about "major meetings", the CAC said that other tasks in its campaign included stopping rumours about epidemics, the economy, public security, as well as the slandering of China's "heroes and martyrs" .

It also said that it would supervise online platforms to improve technologies capable of tracing and containing active and even potential rumour-mongers, such as influential online accounts not affiliated with or run by the state.

"Do a good job of incremental containment, strengthen daily monitoring and analysis," the CAC said.

"When it comes information that is impactful and spread far by non-authoritative sources, take the initiative to the relevant departments for verification, swiftly identify and dispose, strive to nip new rumours and false information in the bud." (Reporting by Eduardo Baptista Editing by Raissa Kasolowsky)