TOKYO, Oct 27 (Reuters) - Short-dated Japanese government bond yields rose on Wednesday, amid pressure from rising U.S. Treasury yields and a relatively weak result at a two-year note auction, while long-term yields were supported by caution about increased government borrowing as Japan votes in lower house elections this weekend. The two-year JGB yield rose 0.5 basis point to an eight-month high of minus 0.105%, pressured by a surge in equivalent Treasury yields to 0.501% in Asia on Wednesday, a level not seen since March of last year. The result of a sale of about 3 trillion yen ($26.3 billion) in two-year notes “was on the weak side, but within the bounds of market expectations,” said a market participant at the domestic securities firm. “Investors probably want to avoid them amid concerns about rising U.S. yields.” The 10-year JGB yield earlier touched 0.105% but fell back to be flat at 0.100%, hovering at levels last seen in April. Benchmark 10-year JGB futures rose 0.11 point to 151.24, with a trading volume of 28,136 lots. New Prime Minister Fumio Kishida has pledged heavy spending for the economy, but faces a crucial test on Sunday as he leads the ruling Liberal Democratic Party into lower house elections. A poor showing could number his days in the top job, with upper house elecions also looming next year. “There are worries about increased JGB issuance related to a scaling up of economic stimulus, and with the election approaching, it’s difficult right now to buy bonds,” said Katsutoshi Inadome, senior bond strategist at Mitsubishi UFJ Morgan Stanley Securities. The Bank of Japan wraps up a two-day policy-setting meeting on Thursday and is widely expected to keep stimulus settings unchanged, with a target of about 25 basis points either side of zero for benchmark 10-year yields. The five-year JGB yield was flat at minus 0.060%, as was the 20-year yield at 0.490%. Traders said some dip buying continued to be seen in superlong bonds. The 30-year yield fell 0.5 basis point to 0.690%, and the 40-year JGB yield dropped 1.5 basis points to 0.735%. (Reporting by Tokyo markets team; Editing by Rashmi Aich)