Baghdad calm after heavy fighting

US forces are targeting Iraqi insurgents

Calm has returned to the Iraqi capital, Baghdad, following some of the heaviest fighting in weeks between US forces and Iraqi insurgents.

Overnight several explosions and heavy gunfire rocked the city as US aircraft flew overhead, witnesses said.

Officials said the activity was aimed at rooting out insurgents carrying out attacks on US forces in the city.

A BBC correspondent says the US military has adopted tougher tactics in recent weeks to combat the insurgency.

'Iron Justice'

Residents in the southern part of the city said their houses shook from the force of the blasts, as military planes and helicopter gunships provided cover for US troops on the ground.

The explosions began at about 0030 local time (2130GMT) and continued for about 20 minutes.

A United States military spokeswoman in Baghdad said the fighting was linked to an operation called Iron Justice.

US Central Command said Operation Iron Justice is "intended to combat corruption both to improve the quality of life for the Iraqi populace and to deny former regime elements illegal sources of income".

Security has been stepped up across Iraq as Christmas approaches, in response to what the US-led coalition describes as specific potential threats.

An explosion was reported outside government offices in the northern city of Irbil on Wednesday morning. There were no immediate reports of casualties.