Iraqi soldiers have started to take over combat positions held by United States troops in the northern city of Mosul.

It is the first move to replace US forces with Iraqi troops in areas outside the capital, which are regarded as insurgent hot spots.

Setting up machine-gun nests on rooftops and at sandbagged checkpoints, the first detachment of Iraqi forces moved into position in an area of Mosul which has seen heavy fighting in recent months.

As the Iraqi soldiers dug in, American troops pulled out.

US military chiefs say the Iraqis will take primary responsibility for security in Mosul, but that American troops would still offer back-up if needed.

The northern Iraqi city has been the scene of a recent upsurge in insurgent attacks.