Iraqi President Saddam Hussein called for a jihad, or holy war, against US-led forces fighting to topple him, but his failure to deliver the speech himself drew fresh questions as to his fate.

Information Minister Mohammad Said al-Sahhaf read the speech on Saddam's behalf.

"Hit them, fight them! They are evil aggressors," he said.

"This aggression is against religion, property, people and dignity" he said of the US-led invasion, adding "this is why jihad is a duty."

The White House said the speech raised "interesting questions," but spokesman Ari Fleischer said that nearly two weeks after the beginning of the war, the mystery over Saddam's fate remains.

Mounting civilian casualties Tuesday stoked international unease at the US-led war, already high after seven women and children were shot dead at a US checkpoint in Central Iraq.

"I'd like to express our regrets to the families of the Iraqis killed yesterday day at the checkpoint near Al Najaf. The loss of any innocent life is truly tragic," said General Richard Myers, chairman of the US joint chiefs of staff.

But he also blamed "the climate established by the Iraqi regime" as contributing to the shooting at a checkpoint at Najaf, 150 kilometersmiles) south of Baghdad, on Monday afternoon.

US President George W. Bush also offered his "regrets" at the deaths of Iraqi civilians, but blamed the casualties on Saddam while backing Defense Secretary Donald Rumsfeld against allegations that he had meddled in military planning to limit the number of troops deployed to Iraq.

Rumsfeld has fervently denied the allegations.

Iraqi officials, meanwhile claimed 23 US or British troops were killed Monday in the southern Iraqi Zhi Qar province.

A spokesman for the International Committee of the Red Cross in Baghdad described the bombings south of the capital as a "horror" that had left dozens of "smashed corpses".

Forty-eight people were killed and over 300 injured by coalition bombing near the farming town of Hilla, 80 kilometres (50 miles) south of the capital, local hospital director Murtada Abbas said.

Fifteen members of a single family were killed late Monday when their pickup truck was blown up by a rocket from a US Apache helicopter in the region of Haidariya near Hilla, the sole survivor of the attack told AFP.

The British and US air strikes on the capital Baghdad left a further 19 people dead and over 100 injured since Monday evening, Information Minister Mohammad Said al-Sahhaf said on the 13th day of the US-led attempt to unseat Saddam and disarm Iraq.

Human rights watchdog Amnesty International asked the United States to undertake a full, independent inquiry into the shooting.

In Brussels the European Commission called the checkpoint killings "a horrible and tragic incident... It is not an isolated incident. Too many civilians have already lost their lives in this war.

But, with US troops on edge after a suicide car bomb attack killed four soldiers near Najaf Saturday, Myers said "the climate established by the Iraqi regime contributed to this incident."

More than 3,000 Arab volunteers in Iraq are ready to carry out suicide missions against the US-led coalition, Iraqi Vice President Taha Yassin Ramadan warned Tuesday.

Meanwhile the air campaign against Iraqi forces around Baghdad intensified, while US marines pushed north toward Baghdad as Iraq beefed up its crack troops guarding the capital against an expected US thrust.

Further west, the US Army's 3rd Infantry Division and 101st Airborne Division were also gearing up for a move against elite Republican Guard units defending the approaches to Baghdad.

Some US commanders have signaled a major tank battle could be shaping up in the next week.

The southern outskirts of Baghdad were pounded by an especially intense bombardment that sent balls of fire and towers of black smoke into the sky.

However British Foreign Secretary Jack Straw warned that as US and British troops advance on Baghdad they will face fierce resistance.

"There may be more setbacks for coalition troops," he said in a speech to the Newspaper Society's annual conference.

In the north, coalition warplanes kept up heavy airstrikes on Iraqi army positions in and around the oil centre of Kirkuk, rebel Kurdish officials said.

In the southern town of Basra, seen as key to controlling the southeast, British troops said they were awaiting reinforcements before making a final push to take the city.

Officials in London said a British soldier was killed on duty in southern Iraq, taking to 26 the British death toll since the start of the war. US authorities say at least 39 US soldiers have been killed.

In Kuwait, air raid sirens sounded for the first time since Saturday. A defence ministry spokesman later said an Iraqi missile had been shot down over southern Iraq.

On the diplomatic front, US Secretary of State Colin Powell arrived in Turkey on a fence-mending mission to underline Washington's commitment to the strategic partnership between the two countries, dented by a series of rows over Iraq.

Relations between the United States and Turkey, the only Muslim member of NATO, have deteriorated since the Turkish parliament on March 1 narrowly rejected US plans to deploy 62,000 troops in Turkey to open a northern front in the war.

Meanwhile, four journalists who went missing last week from Baghdad while covering the Iraq war turned up safely in neighboring Jordan.

The group included correspondent Matthew McAllester, 33, and photographer Moises Saman, 29, -- both of the New York newspaper Newsday -- and freelance photographers Molly Bingham and Johan Spanner.

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SPACE.WIRE