US-led troops fought fierce battles with Sunni and Shi’ite rebels on Thursday and a spate of kidnappings hit foreigners as Iraq descended into bloody chaos not seen since Saddam Hussein’s fall a year ago.A previously unknown Iraqi group said it was holding three Japanese hostages and threatened to ‘‘burn them alive’’ unless Tokyo withdrew its troops from Iraq within three days. Rebels seized two Arabs with Israeli identity cards, shown on a video tape aired by an Iranian television station, and accused them of spying. A Briton was missing after being kidnapped in Nassiriya.Seven South Koreans were seized by armed men while doing missionary work but were later freed unharmed, the Foreign Ministry in Seoul said. They were taken hostage near Baghdad.The top US General in Iraq, Lieutenant General Ricardo Sanchez, acknowledged Najaf and Kut were in the hands of a militia loyal to radical Shi’ite Muslim cleric Moqtada Al-Sadr.Heavy fighting raged in Falluja, Karbala and in Abu Ghraib on the western outskirts of the capital, witnesses said. The upsurge in violence has prompted President George W. Bush’s critics to suggest US forces face a Vietnam-style quagmire, but Sanchez rejected the comparison.‘‘I don’t see any shadows of Vietnam in Iraq,’’ Sanchez told a news conference. He said Sadr’s Mehdi Army militia controlled Najaf and Kut, along with police stations and public buildings, while US-led forces held bases outside the towns.Al Jazeera television aired a video tape showing the three Japanese, including a woman, who are being held by a group calling itself the Saraya Al-Mujahideen (Mujahideen Brigades). They were in civilian clothes.‘‘We tell you that three of your children have fallen prisoner in our hands and we give you two options — withdraw your forces or we will burn them alive and feed them to the fighters,’’ the group said.This week’s sudden Shi’ite uprising, coinciding with the American crackdown on Sunni towns like Falluja and Ramadi, has drawn some expressions of Sunni-Shi’ite solidarity, but it is not clear whether the rebel groups are coordinating, US officials said on condition of anonymity. —Reuters
