Twin car bomb blasts killed 40 people South of Baghdad in an attempt to derail the transition to an Iraqi government in three days, the US military said yesterday. It said 22 people were wounded in Saturday evening?s blasts in Hilla, 100 km from Baghdad.

In a new videotape, militants led by suspected al Qaeda operative Abu Musab al-Zarqawi vowed to behead three Turkish hostages unless Turks stop working with US-led forces in Iraq. Al Jazeera television showed footage of three men crouching before masked gunmen, holding up their passports. It said it had received the footage and a statement from Zarqawi?s Tawhid and Jihad group threatening to kill the men within 72 hours unless ?Turkish forces and companies that support the occupation forces in Iraq? left by the deadline.

Turkey is not part of the US-led force in Iraq but many nationals work as drivers and support staff for US forces. Zarqawi loyalists have staged a series of kidnappings ahead of the June 30 transition. The group beheaded a South Korean last week after Seoul rejected a demand to withdraw its forces from Iraq, and last month decapitated a US captive.

The deadline is before the end of a two-day NATO summit which stards today in Istanbul to be attended by President Bush, who will discuss a NATO role in Iraq. Zarqawi has also claimed responsibility for a series of attacks, most recently a wave of suicide bombings and armed assaults in five cities Thursday that killed more than 100 Iraqis and three US soldiers. More than 20 car bombs have exploded across Iraq this month.

Underscoring the frail security situation, a loud explosion sounded across central Baghdad yesterday and smoke could be seen rising from inside the Green Zone headquarters of the US-led administration, a favored target for insurgents.

<B>?Effective terrorist?</B>

Washington has offered $10 million for Zarqawi?s capture. ?He remains the number one target inside this country. He is a very effective terrorist,? Brigadier General Mark Kimmitt, deputy director of operations for the US military in Iraq, told a news conference in Baghdad Saturday.

US forces have mounted three ?precision strikes? in the rebellious Iraqi city of Falluja over the past week aimed at destroying Zarqawi?s safe houses and killing his followers. Kimmitt said the latest strike, Friday, may have come close to killing the Jordanian-born militant. Senior military officials said 20 to 25 militants were killed in Friday?s strike.

Iraqi guerrillas and tribal leaders in Falluja have denied Zarqawi is in the city, where hundreds of Iraqis were killed in April in fierce fighting between US Marines and guerrillas.

Interim Prime Minister Iyad Allawi said violence could force a delay in national elections to be held by end of January, a key step in the transition to democracy. ?It?s not absolute yet,? Allawi said of the election date, according to excerpts of an interview with CBS News. ?We are committed to elections and one of the tasks is really to work toward achieving these objectives. Security will be a main feature of whether we will be able to do it in January, February or March.?

Writing in London?s Independent Sunday newspaper, Allawi said he would consider an amnesty for Iraqis who resisted US occupation out of a sense of indignation. ?We are drawing up plans to provide amnesty to Iraqis who supported the so-called resistance without committing crimes, while isolating the hardcore elements of terrorists and criminals,? he wrote.

Witnesses in Hilla said the car bombs exploded in a busy street in the largely Shi?ite town shortly after dark. The US military said they were detonated near a mosque.

Andrew Marshall