Tokyo: Japan's benchmark Nikkei index crossed the 51,000 mark for the first time on Wednesday, buoyed by investor enthusiasm over artificial intelligence-related investments.

According to Qatar News Agency, the Nikkei closed up 2.2 percent at a record 51,307.65 points. In contrast, the broader Topix index slipped 0.2 percent, as a stronger yen weighed on export-reliant companies.

The Nikkei had previously breached the 45,000 threshold on September 16 and has climbed sharply since. Shares of Advantest, a Japanese supplier of semiconductor testing equipment to major tech firms, surged 22 percent after the company raised its annual profit forecast by 25 percent, citing robust demand.

SoftBank Group, a major tech investor, rose 3.9 percent, making it the second-largest contributor to the Nikkei's gains. Shares of Lasertec, another heavyweight in the chip sector, jumped 7.7 percent.