The Nikkei stock average closed below the key 9,000 mark Tuesday at a nearly 16-month low as a stronger yen heightened worries about the economy amid inaction by authorities to rein in the currency's advance.

The 225-issue average ended 121.55 points, or 1.33 percent, lower from Monday at 8,995.14, the lowest closing since May 1 last year, when it finished at 8,977.37.

The broader Topix index of all first section issues on the Tokyo Stock Exchange was down 7.06 points, or 0.86 percent, at 817.73.