Japan stocks dropped on Monday morning on the first trading day of the year, as investors already pensive following Wall Street's losses at the end of last year were also disappointed at China's manufacturing data in December that missed expectations.
The 225-issue Nikkei Stock Average plunged 492.30 points, or 2.59 percent, from last Wednesday to end the morning at 18,541.41, Xinhua reported.
The broader Topix index of all First Section issues on the Tokyo Stock Exchange tumbled 31.70 points, or 2.05 percent, at 1, 515.60.
All categories except for mining on the main section retreated, with the biggest decliners comprising foods, rubber products and utilities-linked issues.
Markets here were closed on Thursday and Friday for the New Year break.