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.

Shigeru Ishiba of the long-governing Liberal Democratic Party could face calls to resign if his party fares poorly in Sunday’s Upper House elections.

Japanese voters could unleash political turmoil as they head to the polls on Sunday in a tightly contested upper house election, with rising prices and immigration concerns threatening to weaken Prime Minister Shigeru Ishiba's grip on power.