Japan's Nikkei slumps as AI leaders raise safety concerns; Topix gains

TOKYO, Sept. 14 (Reuters) - Japan's Nikkei share gauge lost ground on Monday, dragged down by technology shares after leaders of major AI companies called for a slowdown in development.

The benchmark Nikkei 225 .N225 slid 0.81% to close at 63,492.99 after falling as much as 2% earlier. The broader Topix .TOPX gained 0.74% to 4,058.21.

Anthropic CEO Dario Amodei on Saturday urged AI companies to slow the advancement of model capabilities, a viewpoint supported in social media posts by OpenAI CEO Sam Altman, xAI chief Elon Musk, and Demis Hassabis, chair of Google's DeepMind division. Altman said separately that OpenAI will not go public in 2026 as it focuses on safety.

SoftBank Group 9984.T, a major investor in OpenAI, led declines on the Nikkei with a 10.72% plunge, its steepest decline in more than two months. Chipmaker Kioxia Holdings 285A.T followed, down 6.37%, and Resonac Holdings 4004.T fell 5.98%.

The largest percentage gainers were Fujitsu 6702.T, up 7.39%, followed by NEC 6701.T, up 6.90%, and Recruit Holdings 6098.T, up 6.35%.

Shares in Chubu Electric Power 9502.T slumped 3.58% after the utility said its president and chairman would both step down following an investigation into falsified seismic data at a nuclear plant.

"In light of these concerns, the outlook for earnings growth has been cast into doubt for stocks relating to semiconductors and the development of AI infrastructure," said Wataru Akiyama, an equities strategist at Nomura Securities. "The drop in the Japanese stock market can be explained almost entirely by this localised drop in AI and chip-related shares."

Markets are also focused on central bank meetings this week, with expectations high for rate hikes by both the Federal Reserve and Bank of Japan. Geopolitical concerns also lingered as the U.S.-Iran conflict continued to disrupt Gulf energy shipments.