The Nikkei 225 index at the Tokyo Stock Exchange was up 99.74 points at 9,681.20 at the start.

As expected, the Federal Reserve announced a new bond-purchase programme to support the sluggish US economy, which sent the dollar lower in New York where the euro almost touched $1.31 before easing back.

But the yen sagged ahead of Sunday's general election in Japan. The opposition Liberal Democratic Party, which wants the Bank of Japan to further ease monetary policy, leads in polls.

"The Fed's decisions did not really surprise anyone, although its comments about expecting rates to remain very low as long as unemployment remains above 6.5 percent were somewhat novel," said Hiroichi Nishi, general manager of equities at SMBC Nikko Securities.

"The bottom line is that it will continue its aggressive steps to foster economic growth," he told Dow Jones Newswires.

Attention has now shifted to hopes for growth in Europe and China as well as the bearish yen, Nishi said.

The dollar was changing hands at 83.27 yen in early Asian trade and the euro at 108.78 yen, almost flat from New York Wednesday afternoon.

The euro bought $1.3069 against $1.3075 in US trade.

The Dow Jones Industrial Average ended down 2.99 points (0.02 percent) at 13,245.45, breaking a five-day winning streak.