The Nikkei stock index briefly topped the 37,000-point threshold for the first time in 34 years on Friday, buoyed by a weaker yen and robust earnings, although gains were limited as some investors moved to lock in recent gains.

The 225-issue Nikkei Stock Average ended up 34.14 points, or 0.09 percent, from Thursday at 36,897.42, its highest close since Feb. 19, 1990. The broader Topix index finished 4.75 points, or 0.19 percent, lower at 2,557.88.

On the top-tier Prime Market, gainers were led by oil and coal, and nonferrous metal issues, while marine transportation, and textile and apparel shares led decliners.

The U.S. dollar hovered in the lower-149 yen range in Tokyo, keeping its strength after briefly hitting its highest level since late November at 149.48 yen in New York overnight amid diverging central bank policies between the United States and Japan.

At 5 p.m., the U.S. dollar fetched 149.39-40 yen compared with 149.28-38 yen in New York and 148.71-73 yen in Tokyo at 5 p.m. Thursday.

The euro was quoted at $1.0780-0781 and 161.05-09 yen against $1.0772-0782 and 160.91-161.01 yen in New York and $1.0780-0781 and 160.32-36 yen in Tokyo late Thursday afternoon.

The yield on the benchmark 10-year Japanese government bond rose 0.025 percentage point from Thursday's close to 0.720 percent, after the debt was sold tracking the overnight gain in U.S. Treasury yields.

The Nikkei climbed over 400 points at one point, but momentum waned after the index surpassed 37,000 due to a lack of fresh trading cues."

The yen's depreciation lifted shares of export-related companies, whose overseas earnings get a boost from the weaker currency when repatriated. Chip stocks also rose, taking a cue from their U.S. counterparts.

A surge for SoftBank Group further bolstered the Nikkei, spurred by the tech investor's announcement of its first quarterly net profit in over a year the previous day.

"The current buying trend is fueled by positive domestic earnings results. However, to sustain this momentum, new catalysts are required," said Masahiro Yamaguchi, head of investment research at SMBC Trust Bank, noting attention is focused on the earnings forecasts of U.S. companies for insights into the demand for regenerative artificial intelligence and semiconductors.

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