US marines marching toward Baghdad encountered heavy Iraqi resistance on Tuesday about 25 kilometers north of the Euphrates River, which they had crossed earlier in the day, correspondents said.
Marines came under cross fire along a road leading north to the Iraqi capital and were harassed by mobile Iraqi units, officers said.
US forces responded with artillery fire and air strikes, according to an AFP reporter travelling with the marines. Up to 150 light armoured vehicles were also called into action.
Earlier Tuesday a column of about 4,000 marines managed to cross the Euphrates River after several days of bloody and costly fighting, which left the road out of Nasiriyah littered with the corpses of dead Iraqi soldiers and burned out vehicles.
One US officer put the number of bodies at more than 100.