* Concerns over supply increase continue to weigh on JGBs

* Investors cautious before five-, 40-year auctions this week

* Two-year/10-year spread hits new 3-½ year high

By Shinichi Saoshiro

TOKYO, Nov 9 (Reuters) - Japanese government bond prices fell on Monday, with the benchmark 10-year yield hitting a 4-½ month high, as investors braced for two debt auctions this week after fiscal worries led to only lukewarm support for a bond sale last week.

A rebound in Tokyo stocks from an early fall also dampened the appeal of JGBs.

"JGBs were hurt by the Nikkei's bounce. The slip in bond futures weighed on cash maturities near the underlying JGBs like the 10-years," said Shinji Ebihara, a quantitative analyst at Mizuho Securities.

The JGB market has been hounded by supply concerns for the past month as it braces for issuance increases to offset low demand for retail bonds, fund an expected tax revenue shortfall and help finance the country's spending plans for the next fiscal year.

These supply worries have hit the 10-year zone particularly hard. The maturity does not have the same kind of core buy-and-hold clientele as other points on the yield curve, though banks and other investors are active in it.