Prime Minister Junichiro Koizumi indicated Sunday that the deaths of two Japanese diplomats in Iraq, possibly at the hands of terrorists, will not change his plan to send troops to the war-torn country.

"I have said Japan will do everything it should regarding Iraq's reconstruction, humanitarian assistance and dispatch of the SDF as well as civilians and government officials," Koizumi told reporters at his residence. "Our basic policy remains the same."

The deaths of the two diplomats were the first involving Japanese since U.S. President George W. Bush declared the end of major combat in Iraq in May.

The incident comes amid government plans to send Self-Defense Forces units to Iraq to aid reconstruction efforts there.

"There is apparently a strong possibility that (the attack) was an act of terrorism," Chief Cabinet Secretary Yasuo Fukuda told reporters after meeting with Foreign Ministry officials. "It is important to show that (Japan) will not flinch from terrorism."

The Foreign Ministry said the two diplomats were attacked with small arms, citing information from the United States. A Tikrit hospital official told Kyodo News the attack probably involved a Russian-made automatic rifle.

For security reasons, their vehicle had nothing -- such as a license plate -- to indicate that Japanese officials were on board, a ministry official said.

Kazunori Tanaka, the Foreign Ministry's parliamentary secretary, headed for Baghdad on Sunday to investigate the incident and ensure the safety of embassy officials. But it was unclear whether he could enter Iraq, apparently due to security reasons.

The two victims were identified as Katsuhiko Oku, 45, councilor at the Japanese Embassy in London, and Masamori Inoue, 30, second secretary at the Baghdad embassy. Their driver, an Iraqi staffer, was seriously injured and later died, the ministry said.

They were heading for a reconstruction meeting in Tikrit, northern Iraq, where the security situation is considered particularly unstable, Foreign Minister Yoriko Kawaguchi said.

Yukio Okamoto, Koizumi's top diplomatic adviser, said he has canceled a visit to Iraq because he "lost his partner" in the country, referring to Oku. Okamoto said he will still visit Iran and Syria.

Oku was working with the U.S.-led Coalition Provisional Authority in Baghdad and its predecessor since April, while Inoue was serving as Oku's interpreter.

U.S. State Secretary Colin Powell called Kawaguchi in the morning to offer his condolences, adding he has ordered U.S. officials in Iraq to provide full support for Japan there, according to the Foreign Ministry.

"Japan has played a critical role in the rehabilitation and reconstruction of Iraq," State Department spokesman Lou Fintor later said in a statement. "Heinous attacks such as these will not weaken our resolve to help build a stable, unified and democratic Iraq."

Koizumi called the families of the two diplomats and offered his condolences.

Kawaguchi said it is a "matter of the greatest regret" that she lost "two distinguished staff members."

"The two were exerting themselves day and night to the utmost under (Japan's) basic policy to support the reconstruction of Iraq despite a severe environment," Kawaguchi said.

She also said the government has no intention of withdrawing its diplomatic staff from Baghdad. There were 11 Japanese government officials in Iraq, including Oku and Inoue, when the incident took place.

The ministry said it asked the U.S. to transfer their bodies out of Iraq by helicopter.

The Foreign Ministry issued a fresh warning Sunday to Japanese in Baghdad, mainly journalists, to leave the nation as soon as possible due to the unstable situation there.

If they must stay, they should take precautions and make sure staff can contact them whenever necessary, the ministry said in a travel advisory.

The ministry also urged all Japanese nationals in surrounding countries to be alert for possible terrorist attacks.

"Although the background of the attack is unclear, there is a possibility of Japanese falling victim to terrorism or unexpected incidents," the travel advisory said.

The ministry said that as of noon Sunday it had confirmed that 21 Japanese -- nine embassy officials, 11 media personnel and one nongovernmental organization staff member -- were in Iraq. It has been unable to confirm if there are other freelance journalists or tourists in the country.

Opposition on attack

Opposition parties on Sunday stepped up their protests over the planned dispatch of Self-Defense Forces personnel to Iraq following the fatal ambush of two Japanese diplomats in northern Iraq.

Katsuya Okada, secretary general of the Democratic Party of Japan, the largest opposition party, slammed the government for what it termed poor safety measures and "lack of foresight."

Saturday's attack came amid strong public concerns about the deteriorating security situation in Iraq.

Okada said there are media reports that the government will soon approve its basic plan for the SDF dispatch at a Cabinet meeting, and urged Prime Minister Junichiro Koizumi to convene a special Diet session to discuss the situation.

Koichi Kato, a former LDP secretary general who has recently rejoined the party, spoke out against the dispatch.

"The war (on Iraq) was a mistake," he told a TV Asahi talk show. Kato, a close ally of the prime minister, won a seat in the Nov. 9 general election for the House of Representatives as an independent but then promptly rejoined the LDP.

The two other smaller opposition parties, meanwhile, shared the views of the DPJ.