China's private sector factories were their busiest in eight months in October with new orders at their highest in a year, according to the final reading of the HSBC China Purchasing Managers' Index (PMI) released on Thursday.

The index rose to 49.5 from 47.9 in September and follows a rise to 50.2 in the official manufacturing PMI for October, published by the National Bureau of Statistics earlier on Thursday.

The twin readings further underpin investor assumptions that recovery is taking hold in China after seven successive quarters of slowing economic growth that leave the world's second-biggest economy on track for its weakest full year of expansion since 1999.

The HSBC sub-index for new orders rose to 51.2, its highest level since October 2011.

The final reading of the HSBC PMI - which captures views mainly of smaller, export-oriented firms in China's vast factory sector - was stronger than a preliminary, or flash, reading of 49.1. Normally the final reading hews closer to the initial flash result.

The reading nevertheless remained below the 50 level that separates contracting from expanding factory activity. It has been below 50 for 12 straight months.

(Reporting By Lucy Hornby; Editing by Nick Edwards)