Fighting intensified Friday in both Baghdad - with more frequent bombing, larger bombs, and successful air strikes - and in Basra, where several thousand civilians tried to escape Friday from the besieged city - only to be fired on by Iraqi paramilitary forces.
Lt. Col. Ronnie McCourt, spokesman for British forces in the Gulf, says Britain's 7th Armored Brigade fired on the Iraqis who were attacking the fleeing civilians.
McCourt says the 7th Armored also worked to evacuate civilians and treat those who were wounded in the Iraqi attack.
Basra - Iraq's second largest city, and one dominated by a different ethnic group than that which rules the Iraqi government - has been struggling with food and water shortages for days.
"We are trying to save the people, return fire and rescue civilians," said McCourt, noting that the Basrans tried to escape in two different places, in the north and the west.
British forces have ringed Basra, in southern Iraq, in hopes of eliminating units still loyal to Saddam Hussein and opening the way for badly needed humanitarian aid.
On at least three separate occasions, including Thursday, British units and coalition aircraft have fired on enemy Iraqi tanks and other armored vehicles that have streamed out of the city.
The British say they are coming to the defense of Shiite Muslims who rose up in the streets against Saddam Hussein's Sunni Muslim regime on Tuesday.
British Prime Minister Tony Blair has promised backing for the insurgents.
Iraq insists there was no uprising.
In Baghdad, the bombing overnight Thursday and into Friday has been frequent, involved the use of two 4,700-pound bunker-buster bombs, which hit an important military target.
CBS News Correspondent Bob Fuss reports the air strike destroyed what U.S. forces say was a "major" command and control center in Baghdad.
U.S. forces have been trying to knock out the ability of the central government in Baghdad to communicate with its forces in the field and also to communicate with the world. Iraqi radio and TV have been frequent targets and have been knocked out for brief periods.
The stepped-up bombing raids on the Iraqi capital could signal that the decisive battle for Baghdad may be drawing near.
Free of constraints imposed by two days of sandstorms, combat aircraft dropped bombs "just about as fast as we can load them," said Capt. Thomas A. Parker, aboard the USS Kitty Hawk in the Persian Gulf.
CBS News National Security Correspondent David Martin reports the Army's Apache helicopters have begun attacking Republican Guard divisions outside the Iraqi capital.
There are five Republican Guard divisions around Baghdad and Saddam's hometown of Tikrit, and three of them are now under constant air bombardment, which could be a sign of where the main ground attack will come.
With a new front opened by paratroopers in the north, U.S. forces are now poised to move on the city from multiple directions.
Wary of engaging the better-armed allies in open desert warfare, the Iraqi government has been goading coalition forces to send ground troops into the capital city.
"The enemy must come inside Baghdad, and that will be its grave," said Iraqi Defense Minister Sultan Hashim Ahmed. "We feel that this war must be prolonged so the enemy pays a high price."
In other major developments: Coalition forces have taken more than 4,000 prisoners of war so far, but U.S. commanders are expressing concern that some Iraqi soldiers allowed to return to their homes are being forced back into service by paramilitary units loyal to Saddam. U.S. Brig. Gen. Vincent Brooks says this happened in Basra, where soldiers from Iraq's 51st Mechanized Division were pressed back into combat duty after their surrender last week. Meeting at Camp David Wednesday and Thursday, President Bush and Britain's Tony Blair vowed to see the war through to victory, but warned of a longer war. Blair accused Iraq of executing captured British troops, a charge the Iraqis denied. In a BBC interview as he arrived back in London Friday, Blair said unseating Saddam will be "tough and difficult... When you've had a whole series of security services repressing the local people, it was never going to be a situation these people were simply going to give up power and go away." The U.S. military is moving more than 100,000 more troops into the Persian Gulf. The Pentagon insists this is part of the planned step-up of forces for the war in Iraq. Officials at U.S. Central Command confirmed that 12 Marines are missing following heavy fighting in the city of an-Nasariyah in southern Iraq. The Pentagon says 26 Americans have been killed in the war so far; 22 Britons have also been reported killed. Figures on Iraqi dead are unknown but widely believed to be over a thousand. Gen. Tommy Franks told Infinity Radio that no weapons of mass destruction have been found to date in Iraq. Iraqi state TV reports that Saddam Hussein chaired a meeting of the ruling Baath Party. The report said the Iraqi leader's top advisers and his son, Qusai, were also there. U.S. intelligence officials say a woman seen at a video of that same meeting - whose date is unknown - is believed to be Huda Salih Mahdi Ammash, one of the government's top biological weapons experts. Desperately needed food and aid for southern Iraq was stranded offshore because of mines Saddam's regime placed in the strategic port of Umm Qasr, military commanders said. The Army's senior ground commander in Iraq, Lt. Gen. William Wallace of V Corps, told the New York Times and the Washington Post that unexpected tactics by Iraqis attacking supply lines are slowing down the campaign. "The enemy we're fighting is different from the one we'd war-gamed against," said Wallace. One area where resistance has been unexpectedly tough is An Nasiriyah, where U.S. Marines and Iraqi forces exchanged tank and artillery fire Friday. Several buildings there, including the power plant, were ablaze. In northern Iraq, U.S. cargo planes have been arriving with military supplies and 200 more troops in the area secured Wednesday by 1,000 U.S. paratroopers. In central Iraq, resupply planes are landing on a restored runway at Tallil Airfield - which was hastily renamed "Bush International Airport" by the American forces who had secured it. The U.S. ambassador walked out of a United Nations debate on the Iraqi war Thursday after Iraq's ambassador accused the United States of trying to exterminate the Iraqi people.