South Korea's key stock market gauge climbed sharply on Monday, driven by continued momentum in semiconductor shares. The rally follows the recent unveiling of OpenAI's new ChatGPT model, codenamed Astra, which has reignited investor enthusiasm for artificial intelligence-related hardware.

The benchmark KOSPI index advanced as much as 3.5% during the session, with heavyweight chipmakers leading the charge. SK Hynix and Samsung Electronics provided the biggest lift to the index, with both stocks jumping at least 4% in early trading.

According to Kim Namho, a fund manager at Seoul-based Timefolio Investment Management, the core driver behind the surge in Korean chip shares stems from optimistic market expectations surrounding OpenAI's latest model. He noted that the same sentiment has also buoyed U.S. semiconductor stocks, reflecting a global reassessment of AI-driven demand for advanced memory chips and processors.

During the morning session, foreign and domestic institutional investors were net buyers of KOSPI-listed shares, while retail investors turned net sellers, taking profits after the recent run-up.

Meanwhile, the tech-heavy KOSDAQ index, which focuses on smaller and mid-sized companies, also posted solid gains, rising as much as 1.5% amid broad-based buying interest.