Three relatives of Iyad Allawi, the acting Iraqi Prime Minister, have been kidnapped in Baghdad, apparently by a group demanding an end to the assault on the rebel stronghold of Fallujah.

As Iraqi anger grew over the assault, a Government spokesman said armed militants had captured Dr Allawi's 75-year-old cousin, Ghazi Allawi, and his cousin's wife and daughter-in-law.

"This is yet another criminal act by terrorists and will not thwart the determination of the Government to combat terrorism," the spokesman, Georges Sada, told Reuters.

The kidnapping coincided with an upsurge of insurgent activity around Iraq as US and Iraqi troops sweep through Fallujah.

Dr Allawi's Government today imposed a curfew on the northern city of Mosul, Iraq's third largest city, after multiple clashes that included attacks against two US convoys. One US contractor was killed, along with three Iraqi policeman and an Iraqi soldier.

A curfew was also declared in the northern town of Baiji, where ten people were killed in clashes between rebel and coalition forces. And six people were killed and four others wounded during clashes in Latifiyah, south of Baghdad.

In Baghdad’s Ghazaliya district, four bystanders were injured during crossfire between US troops and masked fighters.

The kidnapping happened 24 hours after Dr Allawi ordered a full-scale attack on Fallujah to rid the city of rebels and suspected foreign Islamist fighters. A previously unheard of group calling itself Ansar al-Jihad (Holy War Followers) claimed responsibility for the kidnappings in a statement posted on the Internet.

"If the agent government does not meet our demands within 48 hours we will behead them," said the posting on an Islamist website. Its authenticity could not be immediately verified.

Mr Sada gave no details of the circumstances of the kidnappings but a police source said there had been a short gunbattle at the home in the Yarmouk neighbourhood before the hostages were bundled into a car.

"This is a close cousin - Allawi’s father and his father are brothers," Mr Sada said.

Hundreds of Iraqis have been kidnapped by criminal gangs in a wave of abductions in recent months, with wealthy individuals such as doctors and businessmen most regularly targeted. Most are freed after a ransom is paid.

Scores of foreigners have also been seized, with many handed over to Islamic militant groups who have threatened to kill them if political demands are not met. More than 35 foreign hostages have been killed, several by beheading.

In its statement, Ansar al-Jihad demanded the release of all Iraqi prisoners, a demand similar to those made by other militant groups.

Referring to the Muslim month of Ramadan, it said:"With the help of God in this holy month a unit of Ansar al-Jihad kidnapped three relatives of head of the Iraqi agents, Allawi, may God burn him and slaughter him."

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