She flinches just a bit when the air raid siren comes on. Not because it is unusual, but because it is not. And because it reminds her of that day just a few weeks ago.

The sirens sound most every day, once, twice, sometimes more. They are followed by the sound of jet planes soaring overhead. Then the soft puffs of antiaircraft fire off in the distance.

What Nahla Mohammed remembers from that day, however, is not the sirens or the jet planes, but running into her son on the street just after she finished shopping for supper. He asked what she would fix, she recalled. Meat, vegetables and soup, she answered. He headed off, anticipating the family meal.

Ten minutes later, according to a cousin who was there, a powerful blast slammed him to the ground as metal shards sliced through his body. Mohammed Sharif Reda, a 23-year-old mechanic married just two months and planning to build a house for his family, was among four people who Iraqi officials said were killed Dec. 1 in what they call an "undeclared war" being waged here in southern Iraq.

While U.S. troops flow into the Persian Gulf region in preparation for a possible invasion of Iraq, U.S. and British warplanes fire regularly on what the Pentagon describes as military targets. U.S. officials say the bombings and missile attacks are responses to Iraqi challenges to enforcement of the southern "no-fly" zone in place since 1991 -- painting aircraft with air defense radars or shooting at them. But the pace of the attacks has quickened demonstrably in recent months and the Pentagon has broadened its targets to a wide array of command and communications facilities in what analysts see as an effort to weaken Iraq's defenses.

The attack on Dec. 1 destroyed a pair of large vehicles parked in an oil company courtyard in the center of Basra, the country's second-largest city, located near the Kuwaiti border. U.S. military spokesmen said they hit an air defense facility, not an oil company, and in any case never deliberately attack civilian targets. But something obliterated the vehicles here and everyone questioned believes it was the Americans.

"Every day, every day, all the time. Why?" cried Reda's widow, Najila, 25, at the family home around the corner from the Museum of the Martyrs of Hostile Persian Shooting. "I ask you: Why is America bombing?"

Through the first four months of the year, U.S. and British forces struck Iraqi sites in the northern and southern no-fly zones just six times, while in the past four months they have launched about four dozen air raids. So far in December, the U.S. military has reported nine strikes around southern cities such as Kut, Nasiriyah, Amarah and Basra, including one here on Friday.

Iraqi officials complain that U.S. and British aircraft violated their airspace for patrols 1,141 times between Nov. 9 and Dec. 6. In response, Iraqi antiaircraft batteries have fired at U.S. and British planes more than 470 times this year, according to a Pentagon count, although the Iraqis have never succeeded in shooting one down.

The no-fly zones were imposed to protect a Kurdish enclave in the north and rebellious Shiite Muslims in the south from possible attack by President Saddam Hussein's aircraft. While Iraq and several major powers do not recognize the legitimacy of the zones, they have become an inescapable fact of life here.

"Not many people realize that a war has been going on for the last several years in the no-fly zone," said Gen. Amir Saadi, a top Hussein adviser. "The very people that Britain and the United States claim to be protecting, they're killing them, maiming them, depriving them of their normal livelihood and also destroying the infrastructure which is there to serve them."

The Pentagon disputes that and includes a statement at the end of each announcement of another raid: "Coalition aircraft never target civilian populations or infrastructure and go to painstaking lengths to avoid injury to civilians and damage to civilian facilities."

Until recently, U.S. and British warplanes responding to threats from Iraqi forces limited their strikes to gun emplacements, radar facilities and other sites involved in trying to hit them. But Defense Secretary Donald H. Rumsfeld in August ordered his commanders to widen the target list to include more communications centers, command buildings and fiber-optic links.

The more strategic targeting led U.S. forces to strike the Tallil air base, the air defense sector headquarters about 160 miles southeast of Baghdad, a dozen times this fall. With hardened revetments for aircraft, surface-to-air missiles and two major runways, Tallil protects the southern approach to the capital and was a major target during the 1991 Persian Gulf War.

In September, U.S. planes also hit radars at a remote military airfield 240 miles west of Baghdad, far from most antiaircraft fire, in a move that analysts speculated could be intended to open a corridor for Special Forces helicopters to enter the western desert undetected.

The campaign in the south was recently expanded to include propaganda warfare as well. Aircraft dropped 480,000 leaflets at six locations in southern Iraq last week, the seventh time they have conducted such drops in the past three months, according to military officials. The leaflets, distributed in areas where coalition planes recently struck, warned Iraqis against repairing fiber-optic cables and said rebuilding defensive facilities would put their lives in danger.

The leaflets also directed Iraqis to a radio frequency where they could listen to U.S. broadcasts now beamed into the country for several hours a day by military aircraft as they patrol the no-fly zone.

While the zones were established to shield Iraqis from their leader, they have served to embitter at least some of the people, and government officials assert that they even solidify support for Hussein. "When it gets worse and worse, the people will be closer to the leadership," said Lt. Gen. Hadi Abdul Reda, head of civil defense in Basra. "They make me more eager to face the Americans."

"We hate them," said Mesa Ali, 25, a mother of two young boys who lives across the street from the site of the Dec. 1 bombing. The blast shattered her front window, covering her 18-month-old son with broken glass. "They want to get the oil and make us slaves."

"It's a crime," said Ali Abid Hamid, 31, who works at a nearby cement company and helped his cousin get to a hospital to treat a slashed throat after the explosion. "There is no reason to bomb civilians. They want to make problems."

It remains unclear how many civilians have actually been hurt or killed by the recent U.S. and British bombing. Even by Iraqi reports, most targets seem to be military facilities and government officials decline to take journalists there.

The Dec. 1 episode, however, clearly left noncombatants dead and injured, according to interviews with survivors, relatives, witnesses and doctors. The U.S. military reported dropping 23 precision weapons from 13 aircraft in southern Iraq that day in retaliation for antiaircraft fire at warplanes patrolling the northern no-fly zone two days earlier, the first time they had struck in the south for an incident in the north.

The U.S. military said it hit unspecified air defense targets near Basra and Kut, but not an oil installation. Witnesses and survivors, though, said two explosions erupted in the yard of the state-run Southern Oil Co. in the center of Basra between 10 and 11 a.m., about the time U.S. warplanes were reported to be striking. Iraqi officials said four people were killed and 27 injured.

U.S. officials in the past have accused Hussein of positioning mobile air defense units in civilian locations in an effort to prevent them from being destroyed or to draw enemy fire that would kill innocents, thus creating a propaganda victory for Iraq. From the street, about 50 yards away, it appeared clear that at least two large vehicles were demolished by the explosions at Southern Oil. But it was impossible to determine whether they were civilian trucks or mobile missile launchers or radars.

Iraqi officials would not allow an American reporter inside the compound to examine the site.

What was clear was that people such as Watheka Raheem Feyad were in the wrong place at the wrong time. Feyad, 25, a clerk at Southern Oil, had just returned from vacation and was walking between buildings when she was suddenly blown off her feet.

"I felt like I was being sucked up into the air, two to three meters up," she said. "I didn't know if it was a rocket or a missile or a bomb. I didn't know what was the matter. I was afraid and shocked. The noise was very, very loud and I lost feeling in my legs. I closed my eyes because I was so scared."

Two colleagues dragged her away, she said, and she later woke up in the hospital. Her brother, Ali Raheem Feyad, 38, raced to the hospital at 100 mph when he heard the news and was initially told that she was dead. She was not, but she suffered a head injury and multiple fractures of her leg, which is now in a metal splint, and still has shrapnel in her body. She takes six types of drugs, faces several more operations and will need at least a year before she can walk again, according to her doctor.

Mohammed Sharif Reda was not so lucky. Walking outside the gate, he and his cousin were caught in the blast, family members said. His relatives were already angry at Americans, blaming his uncle's death from cancer in March on depleted uranium used in some U.S. weapons in the area.

"They are killing people," Nahla Mohammed, 49, who has lost her son and brother, said, occasionally succumbing to tears as she talked. "Why do they commit such crimes? Why was my son just walking along the streets and died? Why?"

Reda's cousin, Sabah Hassan Mohammed, 23, who was walking alongside him that day, survived but suffered deep gashes in his left leg and deep resentment in his heart. At the hospital last week, he winced in pain and clutched his brother's hand.

"I will get better and I will take revenge, for me and for others," he said. "We are strong. Even if they keep bombing us, we will bear it and we will show them the results."

Nahla Mohammed, 49, lost her son, Mohammed Sharif Reda, 23, in an alleged U.S. airstrike on Dec. 1 in Basra, in southern Iraq.Family members cover their tomato crop on land running alongside the main road from Kuwait to Basra, Iraq.Watheka Raheem Feyad, 25, nearly lost a leg in a Dec.1 airstrike in Basra. Her doctors say it will be at least a year before she can walk again.