The Japanese hostage crisis in Iraq and pension reform weighed heavy on the agenda as House of Representatives by-election campaigning kicked off Tuesday in Saitama, Hiroshima and Kagoshima prefectures.

The three April 25 by-elections -- widely viewed as a litmus test for the July 11 House of Councilors election -- will involve candidates fielded by the Liberal Democratic Party, the Democratic Party of Japan and the Japanese Communist Party.

New Komeito, the LDP's coalition partner, is backing LDP candidates in all the constituencies.

The Saitama No. 8 constituency seat became vacant with the January resignation of LDP member Masanori Arai, who was arrested along with supporters for allegedly violating the Public Offices Election Law during campaigning in November's general election.

The Hiroshima No. 5 constituency seat was left vacant by the death of LDP lawmaker Yukihiko Ikeda and the Kagoshima No. 5 constituency seat by the death of Sadanori Yamanaka, also of the LDP.

Senior officials of the ruling and opposition camps converged on the city of Tokorozawa, Saitama Prefecture, Tuesday morning to stump for their candidates.

Atsushi Kinoshita, 59, of the DPJ is battling an LDP newcomer, lawyer Masahiko Shibayama, 38, while JCP candidate Reiko Yagishita, 57, a former Saitama Prefectural Assembly member, for the Saitama seat.

Kinoshita won a Lower House seat through proportional representation in the November general election, but forfeited it by running in the by-election.

His seat will go to Hiranao Honda, the DPJ candidate next in line on the DPJ proportional representation list.

In his speech, LDP Secretary General Shinzo Abe reiterated the ruling coalition's determination to keep Ground Self-Defense Force troops in Iraq, even though kidnappers who took three Japanese civilians hostage there last week have threatened to kill them if the troops aren't withdrawn.

Abe said that caving in to the kidnappers will only invite more hostage-taking.

"We must win these by-elections in order to strongly push our diplomatic policies (toward Iraq and North Korea) forward," Abe said, while also underlining Prime Minister Junichiro Koizumi's domestic reform initiatives and the recent improvement seen in various economic indicators.

Meanwhile, DPJ leader Naoto Kan said,"It's about time the Self-Defense Forces should scale back their troops in Iraq and evacuate them to Kuwait." He noted that the local security situation has deteriorated and thus urged the gradual pullout.

He reiterated, nevertheless, his party's position that the government should not cave in to the abductors' demands to pull the SDF out.

JCP chief Kazuo Shii called for an immediate withdrawal of the SDF from Iraq.

Kan also criticized Koizumi over the LDP-backed pension reform bills currently being debated in the Diet, saying they would only further aggravate the woes of the pension system by raising premiums and slashing benefits over the next 14 years.

He also slammed Koizumi's drive to increase the financial burden of local governments while reducing central government subsidies to them.

"These by-elections will enable the people to judge the extent to which the prime minister has achieved his general election campaign pledges," Kan said.

Shii also voiced opposition toward the ruling coalition's pension reforms, saying the government should instead cut back on public works and defense expenditure and have big business shoulder a greater burden of social security costs.

The LDP's candidate in Hiroshima is former bureaucrat Minoru Terada, 46, a relative of the late Ikeda.

Mitsuo Mitani, a 44-year-old former secretary to former Prime Minister Kiichi Miyazawa, is running on the DPJ ticket, while the JCP has fielded Susumu Matsumoto, 51, a former member of the city assembly of Takehara.

Terada and Mitani are refraining from making the SDF troops in Iraq an issue in their campaigns, since the constituency hosts a large Maritime-Self Defense Force base. But Matsumoto voiced clear opposition to the SDF dispatch.

Hiroshi Moriyama, who was an Upper House LDP member, is running in the Kagoshima by-election, automatically forfeiting his seat.

The DPJ is fielding Isao Tateyama, 55, a former Hansen's disease patient who was a leading plaintiff in a joint lawsuit demanding compensation from the state for its discriminatory policies.

The JCP candidate in Kagoshima Prefecture is Hiroshi Kayano, 60, a member of the party's prefectural chapter.

Information from Kyodo added