A column of 70 to 120 Iraqi tanks broke out of the besieged southern city of Basra tonight as British troops continued to barrage Iraqi fighters there with artillery fire, British military officials said.

A day after British military officials declared Iraqi positions inside Basra a legitimate military target and prepared to enter the city, it was still unclear whether there was a civilian uprising against the rule of President Saddam Hussein, as British officials reported Tuesday. British Prime Minister Tony Blair said "a limited form of uprising" was underway.

British military officials said the attack on Basra would boost the city's majority Shiite population against the Sunni-dominated Hussein government. But unrest in the city on Tuesday appeared to die down today, and details remained sketchy.

The fighting moved outside Basra tonight as the column of tanks poured out of the city and headed southeast toward the Faw peninsula, British officials reported. The tanks were immediately pounded by coalition aircraft, including British Harrier and Tornado jets. The attack continued late into the night.

[British officials said Thursday morning that coalition forces destroyed most of the armored vehicles with a combination of artillery, airstrikes and ground fire.]

For days, British forces have held off entering the city, hoping to avoid urban warfare and the civilian casualties that would result. But Basra is facing a worsening humanitarian crisis, with electricity and water supplies cut off on Saturday and only partially restored. British military officials now say they may have to enter Basra to defeat the Iraqi military and paramilitary forces that have blended in with the civilian population of 1.3 million.

No humanitarian aid has yet reached the city, though the British plan to start moving water and food supplies to Basra through the newly secured port of Umm Qasr.

"We will do it short steps at a time," said Maj. Steve McQueenie, a British liaison officer at Marine headquarters, which oversees the British forces. "What we have got to do in Basra is make sure civilians are protected."

British officials estimate there are about 1,000 fighters in the city, a mixture of Iraqi soldiers and special militias, including Saddam's Fedayeen.

North of Basra, British forces continued to fire heavy artillery toward the city. A brief barrage could be heard slamming into the city just before 7 p.m., with another slightly longer barrage exactly a half-hour later. After that attack, a bright orange light flashed briefly over the city.

"That is British artillery and that would be aimed at targets in and around the Basra region," said Lt. Chris Head, 24, the platoon commander of the Fusiliers, on the highway about eight miles north of the city center near the Basra International Airport. With pro-Hussein security forces and militia interspersed among the civilian population, "it makes the question of target identification all the harder," Head said.

To aid the British, U.S. warplanes bombed two pontoon bridges in eastern Basra, preventing any Iraqi reinforcements from entering from that direction, or any forces from fleeing that way. British troops also said they captured two busloads of Iraqis believed to be paramilitary fighters in Zubair, just southwest of Basra. The British soldiers chased the buses down the road and stopped them, finding the passengers all dressed similarly and carrying large amounts of money.

On Tuesday, British officials reported signs of an incipient rebellion among the civilian population of Basra, saying that Hussein loyalists had begun firing on their own citizens. But today the details remained cloudy. "Truthfully, the reports are confused, but we believe there was some limited form of uprising," Blair said today. "It is important that we give support to those people in Iraq who are rising up to overthrow Saddam and his deeply repressive regime."

His defense secretary, Geoffrey Hoon, was also vague beyond the fact that "certainly there have been disturbances with local people rising up against the regime." Hoon said it was not clear whether any uprising was still in progress. "We know that there have been attempts by regime militia to attack those people, their own people, to attack them with mortars, machine-gun fire, rifles and so on."

Arab television reporters inside the city reported no signs of disturbance today. "The streets of Basra are very calm and there are no indications of violence or riots. There are no signs of the reported uprising," said a report on al-Jazeera, the Arabic-language television station.

Twelve years ago, in the wake of the Persian Gulf War, the people of Basra rose up in open revolt against Hussein at the encouragement of the United States. But the uprising was brutally crushed and thousands were killed. This time, Basra residents were believed to be remaining cautious about open defiance while Hussein remains in power.

The British troops, who replaced U.S. Marines in southern Iraq after the Americans swept north, have begun what they call their "hearts and minds" efforts on the outskirts of Basra, dismounting from their armored vehicles and conducting patrols on foot today through a village in the oil refinery area south of the city. They said they were able to restore electricity and water to about 300 people in the village.

The British said residents were helping them identify Hussein loyalists and members of his security forces. The soldiers said they were being cautious about responding to such reports, with one saying, "We could be drawn into something we don't want to be in."

"We're winning the hearts and minds of the local people, the vast majority of whom are anti-Saddam Hussein and his regime," said Head, the platoon commander. Speaking of the situation inside the city, he said, "We've been led to believe, by the people we've encountered, that the vast majority of the people are anti-regime."

British troops have also begun the tricky task of trying to disarm the local population. Besides members of the pro-Hussein security forces, many other residents were believed to have firearms, possibly for use in a rebellion against the Hussein government.

The troops said they were seizing arms for the security of their own forces. "We are taking a very robust attitude towards disarmament," Head said. "We consider anyone with weapons a threat to ourselves. We are trying to limit the number of guns and weapons that are out there."

Many of the Fusiliers said they had experience closer to home that would be useful in their current role.

"It's a similar situation to Northern Ireland," said Platoon Sgt. Barry Little, who spent 51/2 years there. "It's a terrorist threat more than an enemy threat."

But, he said, "It's a little bit different here. In Northern Ireland, the Catholics and the Protestants are in clearly defined areas. Here, you have a guy who's carrying a weapon one minute and the next minute he's not."

Glasser reported from Kuwait City. Correspondent Peter Baker with U.S. forces in Iraq contributed to this report.

British soldiers from the 7th Armored Brigade search for looters around an oil refinery southeast of Basra, in an area where troops conducted foot patrols.