Japan's benchmark 10-year government bond yield climbed to its highest level in nearly three decades on Thursday as a renewed surge in oil prices stoked inflation concerns and investors remained cautious about the country's fiscal outlook, according to Reuters.

The yield on the benchmark 10-year Japanese Government Bond (JGB) rose 1.5 basis points to 2.880%, its highest level since September 1996. Bond yields move inversely to prices, meaning rising yields reflect selling pressure in the bond market.

Shorter-dated government bonds also witnessed an increase in yields. The two-year JGB yield, which is highly sensitive to changes in the Bank of Japan's policy rate, rose 1 basis point to 1.44%, while the five-year yield advanced 1 basis point to 1.995%, Reuters reported.

The rise in Japanese bond yields followed a sharp jump in global oil prices after U.S. President Donald Trump indicated that a tentative agreement aimed at ending the conflict with Iran had collapsed. The spike in crude prices pushed U.S. Treasury yields to multi-week highs, adding upward pressure on global borrowing costs.

Investor attention is also focused on Japan's scheduled auction of approximately 2.5 trillion yen ($15.38 billion) worth of five-year government bonds later on Thursday. Improving demand indicators, including a narrowing negative five-year swap spread in recent weeks, could support the auction despite the higher yield environment.

Japan's bond market has been under pressure since the government unveiled an expansive fiscal policy blueprint last month. The spending plans, coupled with a proposal urging the Bank of Japan to align monetary policy with economic growth objectives, have heightened concerns that fiscal expansion could fuel inflation while limiting the central bank's flexibility to tighten policy.

Adding to market uncertainty, according to Reuters, the Japanese government is considering revising the language related to monetary policy in its economic blueprint, raising fresh questions about the future relationship between fiscal and monetary policy.

Analysts believe concerns over increased government spending and its potential inflationary impact have become a major driver of higher Japanese bond yields. With inflation risks resurfacing amid elevated energy prices, investors are closely monitoring both fiscal policy developments and the Bank of Japan's next policy moves.