London (AFP) - Global stock markets plunged further on Tuesday as more gloomy evidence emerged of China's economic slowdown, leading to heavy sell-offs in Asia and Europe.Downbeat data showed factory activity in China hit a three-year low, fuelling concern over the health of the world's number two economy.Tokyo stocks tumbled almost four percent as China woes spread, sending major European bourses sliding by around two percent in late morning deals.China's statistics bureau said its Purchasing Managers' Index of manufacturing activity came in at 49.7 last month, its lowest since August 2012.