U.S. Marines with 3rd Batt., 7th Marines, 1st  Marine Division load an injured Iraqi man on to their vehicle after the bus he was riding in came under fire as it entered a military compound that U.S.  Marines had recently taken in southeast Baghdad on Tuesday, April 8, 2003. (AP Photo/Laura Rauch)

CAMP AS SAYLIYAH, Qatar - U.S. Marines battled to seize Baghdad's second airport Tuesday and were encountering intense resistance in some places around the Iraqi capital, an American general said. Members of the 1st Marine Expeditionary Unit were on the grounds of the Rasheed military airport and were working to secure it after destroying Iraqi tanks and armored personnel carriers, Brig. Gen. Vincent Brooks said.  "There was resistance, most of it leading to it, and there's also resistance beyond it," Brooks said at the daily Central Command briefing in Qatar.  The airport is in a "militarily significant" area near the Tigris River, he said. Taking the airfield would aid efforts to secure the Iraqi capital - and prevent the escape of high-ranking Iraqi officials - as forces loyal to Saddam Hussein turn increasingly to fierce urban combat, Brooks said.

Over Baghdad's international airport, seized last week by U.S. troops, a coalition A-10 "Warthog" warplane was shot down Tuesday, believed to be the first coalition aircraft downed by an Iraqi surface-to-air missile. The pilot ejected safely and was recovered by U.S. ground forces nearby. 

Meanwhile, members of the Army's V Corps entered Baghdad from the north early Tuesday - the first reported movements of U.S. troops in the capital from that direction. Troops were previously known to have entered the capital from the south and southeast. 

Brooks said the V Corps units' defeat of Iraqi forces positioned in the north "opened up an opportunity for us to continue operations on a different line toward the center of Baghdad from a different direction." He refused to elaborate except to say that the strike "may have opened a hole in the north" that commanders might exploit. 

He said most of the Republican Guard defensive line ringing Baghdad's south had been destroyed, and that those Iraqi solders hadn't managed to move into Baghdad. 

Baghdad itself was seeing intense urban combat that can result in deaths and injuries to civilians and bystanders. Two journalists were killed Tuesday when U.S. troops fired on the Palestine Hotel after receiving fire from the area. 

"We know that as we conduct operations inside of Baghdad we should anticipate attacks from unexpected locations, that some of the military actions might be unconventional in nature, whether it's the use of car bombs or whether it's ambushes, the use of snipers, or certainly the consistent pattern we've seen elsewhere of using civilians as shields," Brooks said. 

"We can only be reminded that the risk increases for the population as we do these operations," he added later. "But we have to remain focused on our objective of removing this regime before there's greater loss of life." 

At times, the Iraqi forces include formations of 20 to 60 vehicles, including T-72 tanks or civilian trucks outfitted with military weapons. "Often, all of those vehicles are destroyed - any vehicles that are encountered," Brooks said. 

Soldiers from the Tactical Supply Wing walk along a fuel line at a  forward refuelling dump near the southern Iraqi town of Safwan  Tuesday April 8, 2003. The U.S. military is seeking more commercial quality jet fuel for use in the Gulf, traders said on Tuesday. (AP Photo/Russell Boyce/ Pool)

Parts of the V Corps remained in the center of Baghdad. In addition to the northern thrust, other V Corps units carried out attacks Tuesday morning from the south - battling Iraqi tanks, armored vehicles, artillery and armed civilian vehicles.  It remained unknown whether Saddam and his sons were alive. On Monday, a U.S. warplane dropped four bunker-buster bombs and blasted a smoking crater 60 feet deep at a restaurant where they were believed be meeting.

"Like other places, it is possible that we may never be able to determine exactly who was present without some detailed forensic work," Brooks said. "That's one of the circumstances that we have to deal with as we go through this campaign."