TOKYO: Japanese government bond prices were weaker on Thursday, as the Nikkei share average briefly broke above the 18,000 mark for the first time since December last year.

The results of JGB buying operations by the BOJ on Thursday also showed stronger selling pressure in the 10 year and longer zone.

The offer-to-cover ratio in the 10- to 25-year zone came in at 3.18 times, the highest level since Oct 27 last year, when it was 4.31 times.

In its buying operation the 25- to 40-year zone rose to 2.64 times, the highest level since 3.49 on Feb 6.

The recent high volatility in the JGB market has made it very difficult for dealers and short-term players to hold JGBs for one day or longer to sell them directly to the BOJ.

The current five-year JGB yield rose 0.5 basis point to 0.125 percent ahead of Friday's five-year JGB auction.

The 10-year yield also added 0.5 basis point to 0.395 percent while the 20-year yield rose 1.0 basis point to 1.200 percent.

At one point, it climbed to 1.205 percent, the highest level since Nov 27.

Copyright Reuters, 2015