Japan's prime minister has said his country will not withdraw its troops from Iraq despite the kidnapping of three Japanese by Iraqi insurgents.
Picture of the frightened hostages are splashed across Japan's papers
The insurgents have threatened to kill them unless Japan withdraws its forces from Iraq within three days.
The hostages' families are in the capital, Tokyo, to plead for their lives, but the government said it saw no reason to pull out its 500 soldiers.
Mr Koizumi said: "We should not give in to these despicable threats..."
South Korea has meanwhile warned its citizens not to go to Iraq, after the abduction of seven South Korean missionaries, who were later released unharmed.
But the government in Seoul said it would go ahead with plans to send 3,600 troops to Iraq.
A Syrian-born Canadian and two Palestinians are also among foreign hostages being held by Iraqi insurgents.
Meanwhile, on the anniversary of the toppling of Saddam Hussein, US-led coalition soldiers across Iraq have been engaged in fresh clashes with Sunni and Shia militants.
The BBC's Jonathan Head, in Tokyo, says that in safe and orderly Japan, pictures of three terrified Japanese civilians being held hostage by a group calling itself the Mujahideen Brigades are a source of nationwide anguish.
Television networks repeatedly aired dramatic video of the two aid workers Noriaki Imai, 18, and Nahoko Takato, 34, and photojournalist Soichiro Koriyama, 32.
"The government in crisis" - the headline in one leading newspaper this morning, and it is no exaggeration, our correspondent says.
Mr Koizumi took a huge political gamble when he sent Japanese troops into Iraq earlier this year - much of the Japanese public opposed it.
The government cannot be sure how long public opinion in Japan can withstand the agony of a prolonged hostage crisis, our correspondent adds.
More US soldiers killed
Meanwhile, the Arab League has offered to organise talks in Cairo between the American-led coalition running Iraq and the groups that it is fighting against.
Recent violence has left up to 300 Iraqis and at least 30 coalition troops dead. The US army said six of its soldiers had been killed in Iraq in the past three days.
Coalition troops are engaged in clashes with insurgents across Iraq
The league's secretary-general, Amr Moussa, said the core issue that must be addressed was the deteriorating relationship between the coalition, its occupation forces and the Iraqi people.
The US says its forces no longer have full control over two southern towns after nearly a week of fighting Shia militia who support the cleric Moqtada Sadr.
Rebels were in partial control of the city of Najaf, and fully controlled the town of Kut after pushing out Ukrainian troops, US military commanders said.
And US troops in Iraq trying to take control of the mainly Sunni city of Falluja have called for reinforcements, after continued heavy fighting.
There are reports of bodies in the streets and of makeshift clinics being set up, with medical supplies scarce.
Hospital workers say up to 300 Iraqis have been killed in Falluja since the American assault began, although these reports are unconfirmed.
The US has also rushed troops to the holy city of Karbala, to reinforce the hard-pressed Bulgarian and Polish troops based there.