The commander of US ground forces in Iraq acknowledged Thursday that four of the country’s most populous provinces are not yet secure enough to hold national elections.

Seven United States soldiers were killed in Baghdad on Thursday when a roadside bomb hit their Bradley armoured fighting vehicle, killing all aboard, a military spokesperson said.

In a separate development, it has emerged that 18 Iraqi men recruited to work at a US base near Mosul have been murdered. Their bodies were found in a field outside the northern city.