** Hong Kong-listed shares of WuXi Apptec 2359.HK drop 6% to HK$114, their lowest level since March 30

** Stock posts its biggest intraday pct gain since September 4

** WuXi's Shenzhen-listed stock 603259.SS falls 5.6% to 90.61 yuan, its lowest level since March 24

** The U.S. on Monday added Chinese e-commerce giant Alibaba 9988.HK, internet search provider Baidu 9888.HK and automaker BYD 002594.SZ to a list of companies it believes are aiding Beijing's military, in a move that could inflame tensions between the countries

** Other companies in the list include WuXi AppTec, RoboSense Technology 2498.HK and Unitree

** A WuXi AppTec spokesperson told Reuters that the company's inclusion on the list was "clearly a mistake" and that it would take immediate actions to "correct this erroneous designation"

** Alibaba said it is not a Chinese military company nor part of any military-civil fusion strategy and it will take all available legal action against attempts to misrepresent the company

** Hong Kong-listed shares of Alibaba slip 0.4% and RoboSense down 0.2%, while Hong Kong stock of Baidu climbs 1.4% and BYD 1211.HK gains 1.5%