The benchmark Nikkei stock index extended its winning streak to the 12th straight day on Wednesday, as investor sentiment was bolstered by a strong showing on Wall Street overnight and hopes for upbeat corporate earnings reports.

The 225-issue Nikkei Stock Average added 26.93 points, or 0.13 percent, from Tuesday to end the day at 21,363.05.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, gained 1.27 points, or 0.07 percent, to finish at 1,724.64.

Brokers said that investors were betting on solid corporate earnings from Japanese companies ahead of earnings season swinging into full gear later this month.

They said that blue chip issues were being snapped up by foreign investors, particularly stocks of firms with an exposure to international markets, owing to expectations for increased profits based on performance as well as favorable exchange rates.

Some individual and institutional investors, meanwhile, opted to secure gains following the market's recent rally, which capped overall gains, market strategists added.

By the close of play, pharmaceutical, land transportation, and oil and coal product-linked issues comprised those that gained the most, and falling issues beat rising ones by 1,226 to 717 on the First section, with 88 ending the day unchanged.

On the main section on Wednesday, 1,357.76 million shares changed hands, dropping from Tuesday's volume of 1,593.64 million shares.

The turnover on the third trading day of the week came to 2,284.0 billion yen (20.35 billion U.S. dollars).