BEIJING (REUTERS) - China will not tolerate anything that challenges the bottom line of the "one country, two systems" formula that governs Hong Kong, a senior China parliamentary official said on Friday (Nov 1).

Hong Kong was an important part of discussions at a plenum of the ruling Communist Party which finished on Thursday, said Mr Shen Chunyao, head of the Basic Law Committee of the Parliament's standing committee.

Beijing also will curtail infiltration activities by foreign forces, Mr Shen said.

China will ensure Hong Kong's prosperity and stability, and protect national security in the face of unrest there, the Communist Party said on Thursday after the plenum, though it unveiled no new policy steps.

Hong Kong was handed from British to Chinese rule in 1997 under the "one country, two systems" formula, which guarantees freedoms not granted in mainland China.

Since June, protesters have taken to the streets of the city in sometimes violent demonstrations in response to perceived Chinese meddling with those promised freedoms.