"Elements of the 1st Marine Division crossed the Diyala river and will link up with the 3rd Infantry Division today," said Lieutenant Colonel Ted Ohnemus.

Clearing the bridge across the Diyala, which runs east of the Iraqi capital, "caused a delay of a couple of days," said Ohnemus, a liaison officer with the First Marine Expeditionary Force.

Ohnemus said there was "probably a few kilometres, it's not very much" of an area that had still not been sealed.

The Marines overcame the obstacle by apparently using their own bridge, he added.

Ohnemus said the 269 Battalion of the 3rd Brigade Combat Team "will link with the 3rd Battalion of the 7th Marines" to close the circle around Baghdad.

"As we continue to seize the initiative, we have expanded our area of operations in the city but we haven't added any forces," Major Mike Birmingham, public affairs officer for the 3rd Infantry Division, said earlier.

"We just continue to seize the initiative, will continue to push. Hopefully the regime will fall. It's just a matter of time."

Members of the division's 3rd Brigade were involved in the operation to seize control of Iraqi President Saddam Hussein's vast Republican Palace complex while the 2nd Brigade was conducting operations in downtown Baghdad.

Some 6,000 US troops have set up base around the airport on the southwestern rim of the capital, from where they have been launching raids into the city center.

Birmingham said that the US forces had come under artillery and rocket-propelled grenade fire from members of Saddam's elite Special Republican Guard, but added there were "no (US) casualties reported" overnight.

Later in the day, General Buford Blount said US forces were encountering fire from several points in the city, including the zoo.

"This morning it was hotter. Counterattacks from the east side," said Blount, commander of the 3rd Infantry Division.

The resistance involved 40 to 50 Iraqi trucks and 250 men, including people in civilian and military clothes.

"The trucks have been destroyed," said Blount. "They're (US forces) still taking fire around the palace compounds, around government areas and the zoo."

A-10 Thunderbolt ground attack aircraft attacked a Special Republican Guard compound near the airport Tuesday morning.

An AFP photographer on the scene saw one Iraqi tank dug deep inside the compound and US soldiers conducting building-to-building searches.

One building was completely demolished, while a large metal statue of Saddam Hussein on a horse was still standing, the photographer saw.

Birmingham said that the presence of the US troops in the center of the capital sent a message to the Iraqi people that Saddam's days were numbered.

"They are seeing their leaders are lying to them. The regime is not in control."

US tanks fought their way across the presidential palace compound Tuesday amid heavy exchanges of tank, artillery and gun fire, AFP correspondents witnessed.

After five hours of intense clashes, two US Abrams tanks rolled out of the northern entrance of the compound and took up position on the adjacent Al-Jumhuriya bridge.

Exchanges of fire then broke out with Iraqi forces on the east side of the river for the first time since US armour stormed into the city centre early Monday.

SPACE.WIRE