TOKYO, July 2 (Reuters) - Japanese government bond yields rose on Tuesday as investors awaited details on the Bank of Japan's plan to reduce its monthly bond buying.

The 10-year JGB yield rose 2.5 basis points (bps) to 1.085%. The five-year yield rose 1.5 basis points to 0.605%.

"Until the BOJ announces the details on how it will cut its bond-buying amounts, the yields will be on upward trend," said Miki Den, a senior Japan rate strategist at SMBC Nikko Securities.

At a policy meeting last month, the BOJ decided to announce in July a detailed plan on how it plans to reduce its huge bond buying and scale back its nearly $5 trillion balance sheet.

Japan bond market participants expect the central bank to trim bond purchases by roughly $100 billion in the first year under a quantitative tightening (QT) plan set for release this month, according to a survey conducted by Reuters.

On Tuesday, the market witnessed a relatively strong outcome of an auction for 10-year JGBs, with its lowest bidding price being higher than market expectations.

The yields on bonds with super long maturities rose ahead of an auction for 30-year bonds later in the week, as investors sold the bonds to buy them back at the auction, Den said.

The 20-year JGB yield rose 2.5 bps to 1.92%. The 30-year JGB yield rose 1.5 bps to 2.255%.

The 40-year JGB yield rose 1 bp to 2.390%.

The two-year JGB yield rose 0.5 bp to 0.36%. (Reporting by Junko Fujita; Editing by Janane Venkatraman )