TOKYO -- Japanese were voting Sunday for seats in the smaller of Japan's two parliamentary houses in a key election with Prime Minister Shigeru Ishiba and his ruling coalition facing a possible defeat that could worsen the country's political instability.

By Tim Kelly and Mariko Katsumura TOKYO (Reuters) -Japanese voters headed to the polls on Sunday in a tightly contested upper house election that could unleash political turmoil, with rising prices and immigration concerns threatening to weaken Prime Minister Shigeru Ishiba's grip on power.

Japanese voters headed to the polls on Sunday in a tightly contested election amid public frustration over rising prices and the imminent threat of US tariffs. The ruling Liberal Democratic Party (LDP) and its junior coalition partner Komeito need to secure a combined 50 seats to retain an overall majority in the upper house but the latest polling shows they might fall short.