Asian and European stock markets sank Wednesday, deepening the week's losses as investors banked profits from recent gains, while wearily eyeing Brexit developments.

Hong Kong and Tokyo spearheaded an Asian market plunge, with technology and energy firms the biggest losers after Wall Street dropped on Tuesday.

Europe meanwhile tripped out of the gates Wednesday and was still languishing in the red around midday.

"It's profit taking until the end of the year," Will Hamlyn, senior equity investment analyst at Manulife Asset Management, told AFP when asked about the cause of this week's heady losses.