An 'organised group of attackers' ambushed a United States tank patrol north of Baghdad on Friday, sparking a battle that killed at least 27 of the assailants, CNN reported in its website.

The attackers fired rocket-propelled grenades at the 4th Infantry Division patrol in Balad, the report said. The tanks immediately returned fire, killing four attackers and forcing the rest to flee.

Tanks and Bradley fighting vehicles, backed by Apache helicopters, pursued the attackers, killing 23.

US forces conducted a wide-ranging mission -- dubbed 'Operation Peninsula Strike' -- near Balad earlier this week, capturing almost 400 suspected Iraqi fighters loyal to Saddam Hussein's former regime.