Tokyo stocks extended their winning streak for a fifth straight session, with a key index renewing the highest closing level in six years, helped by overnight gains on Wall Streets and the yen's depreciation against major currencies the US dollar. The benchmark Nikkei 225 Stock Average on the Tokyo Stock Exchange (TSE) advanced 18.91 points, or 0.12 percent, from Friday to 15,889.33, the highest close since Dec 12, 2007. Japanese financial markets were closed Monday for a national holiday, while in the morning, the Nikkei index briefly topped the psychologically important 16,000 mark for the first time in six years, but the broader Tokyo Stock Price Index, which includes all First Section issues on the TSE, edged down 4.09 points, or 0.32 percent, to 1,257.55. On Monday, the Dow Jones industrial average closed at all-time highs again on expectations for a US economic recovery. The yen's depreciation against the US dollar and the euro also prompted Japanese investors to buy export-oriented issues in Tokyo. The weak yen supports exports by making Japanese products more competitive overseas and increase the value of repatriated overseas earning. In the currency market, at 4 p.m. (0700 GMT), the US dollar fetched JPY 104. 22-26 against JPY 104.06-16 in New York at 5 p.m. Monday and JPY 104.42-43 in Tokyo at 5 p.m. Friday.