Tokyo, Apr 6 (IANS): Campaign for an upper house by-election for a seat representing Japan's southwestern prefecture of Oita started on Thursday, with key issues including child-rearing support, and measures to tackle the country's soaring prices.

The start of the Oita race will be followed by the kickoff of campaigning on April 11 for four by-elections for the House of Representatives, or the lower house of parliament, reports Xinhua news agency.

The five by-elections will be held on April 23, along with the second round of local polls to select mayors and assembly members across the country.

The electoral tests are closely watched as an interim evaluation for the government of Prime Minister Fumio Kishida, also president of the ruling Liberal Democratic Party, as he faces a declining approval rating.

The results of the elections are likely to affect Kishida's decision on whether to dissolve the lower house for a snap election, pundits said, noting that his Liberal Democratic Party is eager to secure at least three of the five seats, the number previously held by the ruling party.

The by-election in Oita is to fill the vacancy left by independent Kiyoshi Adachi, who won the seat with support of the Constitutional Democratic Party of Japan and other opposition forces but chose to run for the governorship in the prefecture.