Iraqi forces swept through Baghdad yesterday, erecting checkpoints and searching vehicles as they launched the largest offensive of its kind since Saddam Hussein's ouster, but insurgents hit back with suicide bombings and ambushes that killed at least 21 people, including a British soldier.

　　The first of more than 40,000 soldiers and police, who are being supported by US forces, searched hundreds of vehicles and raided several houses, described as "terrorist dens" in Baghdad's Dora neighborhood, arresting several suspects, army Captain Ihssan Abdel-Hamza said.

　　"Operation Lightning" was launched as a direct challenge to the bloody wave of militant attacks that have killed more than 700 people since the April 28 announcement of Iraq's new Shiite-led government.

　　"We set up these checkpoints in order to arrest all those insurgents trying to destroy this country and we will hit them with an iron fist," said Iraqi army Sergeant Ali al-Khazali while manning a highway checkpoint in Dora.

　　But insurgents defied the offensive, launching a series of coordinated attacks in western Baghdad's Abu Ghraib, Amariyah and Khadra neighborhoods, attacking two police stations, an Iraqi army barracks and a checkpoint.

　　It was not know how long the Operation Lighting would last, and its success or failure would be an indication of how long it would take for Iraqis to take control of their own security, a key part of the US exit strategy from Iraq.

　　Britain's The Sunday Times reported yesterday that Abu Musab al-Zarqawi, the leader of al-Qaida in Iraq, has left the country after being wounded in a missile attack and was thought to be in Iran. The paper said it obtained the information from an unidentified senior insurgent commander with close contacts to al-Zarqawi's group.

　　Tehran rejected the newspaper report that al-Zarqawi was in Iran.

　　A police official said three civilians were killed during the brazen attacks and 15 wounded, including 10 soldiers and policemen. About 50 gunmen fired rocket-propelled grenades, mortars and machine guns at Baghdad's police Major Crime Unit in Amariyah at about 3:30pm in a battle that lasted at least 30 minutes, another police official said.

　　Several minutes later, a car bomb exploded at a nearby Amariyah army barracks and an Iraqi military-controlled checkpoint in Abu Ghraib, the focus of a recent Iraqi-US military operation, dubbed "Operation Squeeze Play," which aimed at ridding the volatile area of militants. It was the prelude to the current Iraqi-led Operation Lightning.

　　At about 4pm, gunmen attacked Khadra police station during a 15-minute firefight, said police Lieutenant Majid Zaki.

　　In Tokyo, a Japanese man confirmed on Saturday that his older brother, a security worker kidnapped in Iraq, was the dead man shown on an extremist Islamic militant group's Website, an official said.

　　A three-minute video posted on Friday on the Website of Islamic militant group Ansar al-Sunnah Army showed footage of a bloodied Asian man lying on his back with arms outstretched, as well as documents with his name and photographs of his face. A statement, accompanied by Koranic verses, identified the dead man as Japanese hostage Akihiko Saito.

　　Saito, a 44-year-old security consultant, was working for Hart Security Ltd, based in Cyprus, when he and four other foreign workers were ambushed in the vast Anbar province west of Baghdad.

　　Saito became the sixth Japanese national to be killed in Iraq since the US-led war.

　　(The Associated Press)