Fire was rising from a building in the city center. It was not immediately clear what targets had been struck.

A number of explosions also rocked the northwest outskirts of the capital about 20 minutes later, an AFP reporter said, after an apparently dramatic increase in US-led bombing raids on Baghdad and its rim Thursday.

And at about 3:15 (2315 Thursday), AFP correspondents heard anti-aircraft fire and at least a dozen explosions on the western outskirts of the capital with artillery pounding on the southern approach to the city.

Violent blasts had been heard earlier southwest of Baghdad, the site of Saddam International Airport, following US reports that coalition forces had captured part of the site in heavy fighting.

The airport lies just 20 kilometers (12 miles) from central Baghdad.

Artillery fire was heard Thursday evening on the southern outskirts of Baghdad for the first time as US forces said they were approaching the capital.

Repeated air strikes pounded the southern edges of the city in the early evening and massive, booming explosions could be heard from the city center.

That was followed at about 5:30 pm (1430 GMT) by heavy bombardment of the western outskirts, which continued for more than seven minutes.

SPACE.WIRE