Insurgents bombed a bridge over a major highway in Iraq for the third consecutive day on Tuesday. Bridge bombings have been on the rise in recent months, but this week's attacks indicate a new campaign against key transport routes may have begun.

Tuesday morning's attack partially destroyed a bridge linking the villages of al-Qariya al-Asriyah and al-Rashayed in northern Babil province on the main north-south highway about 35 miles south of Baghdad, and just six miles south of the bridge destroyed on Sunday.

The AP reports local police said about 60% of the bridge was damaged, though cars could still pass over it via one lane. But debris from the blast fell on the main north-south expressway below, further complicating efforts to reopen that main artery, closed after Sunday's blast dropped masses of concrete onto the roadway.

Three US soldiers were killed in Sunday's bridge bombing. A suicide car bomber struck a major bridge in Iraq's volatile Diyala province on Monday, cutting the span over the Diyala River, but causing no casualties. The destruction reportedly requires traffic to be detoured through al Qaeda-dominated territory.

In other recent bridge attacks, in mid-May a double car bomb brought down the Badoush bridge spanning the Tigris in Mosul, and others severely damaged the Old Diyala Bridge and the nearby New Diyala Bridge, which span the Diyala River, a tributary of the Tigris in southern Baghdad.

In mid-April, the 75-year-old British al-Sarafiya bridge in Baghdad was cut in two by a truck bomb, plunging a number of cars into the Tigris and killing approximately a dozen of Iraqis.

Ordinary Iraqis have begun relying on small ferries to cross rivers, but the destruction of key arteries has the potential to disrupt the transport of military supplies and manpower.