South Korea's Kospi plunged 2.2 percent at midday after 47,000 Samsung employees announced they would go on strike on Thursday. Samsung shares fell 3 percent on the announcement.
In Japan, the Nikkei 225 and Topix fell 1.3 percent and 1.7 percent, respectively.
Movements in China were slightly smaller, with Shenzhen down 0.8 percent and Shanghai down 0.6 percent.
Hong Kong's Hang Seng fell 0.9 percent.
