The benchmark Nikkei 225 index was up 0.36 percent or 76.87 points at 21,468.97 while the broader Topix index was up 0.52 percent or 8.10 points at 1,566.09.

"A risk-on sentiment is likely to continue on the backdrop of a cheaper yen against the dollar, while caution remains ahead of the ECB meeting" later this week, Okasan Online Securities said in a commentary.

The dollar fetched 107.57 yen in early Asian trade, against 107.53 yen in New York late Tuesday.

Automakers were higher, with Nissan trading up 2.69 percent at 716.3 yen, Honda up 1.82 percent at 2,841.5 yen and Toyota up 0.79 percent at 7,240 yen.

Some other exporters were higher, with Panasonic up 1.25 percent at 892.5 yen and Nikon up 1.30 percent at 1,400 yen.