** Ubtech Robotics 9880.HK jumps 7.5% to HK$85.7; on track for biggest one-day pct gain since March 4

** Chinese humanoid robot maker says its chairman Zhou Jian and other senior executives bought co's H-shares in open market with their own funds on April 1

** Adds move aims to reflect their full confidence in firm's business development and prospects and that the shareholding may increase further when appropriate

** Stock up 52.8% YTD

(Reporting by Donny Kwok)

((donny.kwok@thomsonreuters.com))