TOKYO, Dec 16 (IFR) - Japanese government bond prices mostly edged down in relatively quiet trading as the Bank of Japan refrained from any purchases under its asset-buying program on Monday, contrary to market expectations.

A few investors bought the current 10-year JGBs on dips in the morning session, sending its yield down from its intraday high of 0.690 percent to 0.685 percent, flat from Friday.

But other domestic real money accounts stayed largely sidelined in the morning session on caution ahead of Tuesday's monthly 20-year JGB auction, the Dec. 17-18 Federal Reserve policy meeting and the BOJ's Dec. 19-20 policy meeting.

Earlier on Monday, the JGB market shrugged off the BOJ's quarterly tankan business sentiment survey. Japanese business confidence improved in the three months to December for a fourth straight quarter, boding well for the government's stimulus policies aimed at ending years of deflation.

At midday, the yield on the current 5-year JGB was up 0.5 basis point from Friday at 0.215 percent, while the 10-year yield was flat at 0.685 percent.

In the superlong zone, the 20-year yield was up 0.5 basis point at 1.550 percent, compared with 1.545 percent earlier. The 30-year JGB was yet to be actively priced.

Lead March JGB futures moved in a 143.75-143.98 range before finishing the morning session down 0.02 point from Friday at 143.83.