A suicide bombing in a crowd welcoming former Prime Minister Benazir Bhutto killed at least 126 people Thursday night, shattering her celebratory procession through Pakistan’s biggest city after eight years in exile.

Two explosions went off near a truck carrying Bhutto, but police and officials of her party said she was not injured and was hurried to her house. An Associated Press photo showed a dazed-looking Bhutto being helped away.

Officials at six hospitals in Karachi reported 126 dead and 248 wounded, making it one of the deadliest bomb attacks in Pakistan’s history.

Bhutto flew home to lead her Pakistan People’s Party in January parliamentary elections, drawing cheers from supporters massed in a sea of the party’s red, green and black flags. The police chief said 150,000 were in the streets, while other onlookers estimated twice that.

The throngs reflected Bhutto’s enduring political clout, but she has made enemies of Islamic militants by taking a pro-U.S. line and negotiating a possible political alliance with Pakistan’s military ruler, President Gen. Pervez Musharraf.

An estimated 20,000 security officers had been deployed to protect Bhutto and her cavalcade of motorized rickshaws, colorful buses, cars and motorcycles in the streets of Pakistan’s largest city.

Authorities had urged Bhutto to use a helicopter to reduce the risk of attack amid threats from extremists sympathetic to the Taliban and al-Qaida, but she brushed off the concerns.

”I am not scared. I am thinking of my mission,” she had told reporters on the plane from Dubai. ”This is a movement for democracy because we are under threat from extremists and militants.”

Last month, Bhutto told CNN she realized she was a target. Islamic militants, she said, ”don’t believe in women governing nations, so they will try to plot against me, but these are risks that must be taken. I’m prepared to take them.”

Leaving the airport, Bhutto refused to use a bulletproof glass cubicle that had been built atop the truck taking her to the tomb of Pakistan’s founding father, Mohammed Ali Jinnah, to give a speech. She squeezed between other party officials along a railing at the front and rode high above the street.

Her procession had been creeping toward the center of Karachi for 10 hours, moving at a snail’s pace while dancing and cheering supporters swarmed around the truck, when a small explosion erupted near the front of the vehicle.

That was quickly followed by a larger blast just a few feet from the truck, setting an escorting police van on fire and breaking windows in Bhutto’s vehicle. Party members on top of the truck scrambled to the ground, one man jumping while others climbed down a ladder or over the side.

”Evidence available at the scene is suggesting it was a suicide bombing and … exploded near police vehicles destroying the two police vans escorting Benazir Bhutto’s truck,” police officer Raja Umer Khitab said. He said several policemen died.

At the scene of the attack, bodies lay motionless in the street, under a mural reading ”Long Live Bhutto” on the side of the truck.

”People were shouting for help but there was no one to help them out. It smelled like blood and smoke,” said AP photographer B.K. Bangash, who was 150 feet from Bhutto’s truck when he heard a small blast just before midnight.

The bombs exploded just after the truck crossed a bridge about halfway from the airport to the tomb.

Pools of blood, broken glass, tires, motorcycles and bits of clothing littered the ground. Men carried the injured away from burning cars. One bystander came upon a body, checked for signs of life, and moved on.

Some of the injured were rushed into a hospital emergency room on stretchers, and others were carried in rescuers’ arms. Many of the wounded were covered in blood, and some had their clothes ripped off.

The United States condemned ”the violent attack in Pakistan and mourns the loss of innocent life there,” said Gordon Johndroe, foreign affairs spokesman for President Bush. ”Extremists will not be allowed to stop Pakistanis from selecting their representatives through an open and democratic process.”

Richard Haass, president of the New York-based Council on Foreign Relations, said the attack reveals ”one of the fundamental realities of Pakistan today is that the government is not in total control of the country.”

He said he did not think Musharraf would declare a state of emergency, saying there were more serious challenges to state authority recently, like the standoff between militants and police at Islamabad’s Red Mosque.

The bloodshed marred what had been a jubilant day for Bhutto. She received a rapturous welcome from tens of thousands of supporters, many craning from tree branches and foot bridges to glimpse her return.

The 54-year-old politician wept for joy.

”I feel very, very emotional coming back to my country,” Bhutto told AP Television News at the airport, after passing under a Quran held over her head as she got off the plane.

”I dreamt of this day for so many months, and years. I counted the hours, the minutes and the seconds just to see this land, sky and grass. I’m so emotionally overwhelmed,” she said, dressed in green with a white head scarf to match Pakistan’s national flag.

Bhutto had paved her route back to Pakistan through negotiations with Musharraf, a longtime political rival whose rule she has often condemned but whose proclaimed mission to defeat Islamic extremism she shares.

The talks yielded an amnesty covering the corruption charges that made Bhutto leave Pakistan, and could lead to a political alliance uniting moderates in parliamentary elections for a fight against militants allied with al-Qaida and the Taliban.

U.S. officials are believed to still favor Musharraf, despite his sagging popularity, over his two main civilian rivals _ Bhutto and Nawaz Sharif, the elected premier ousted by the general in a 1999 coup and sent back into exile when he tried to return last month.

Washington considers Musharraf a source of stability in a nuclear-armed country fighting militants along the border with Afghanistan, an area where Osaka bin Laden may be hiding.

Still, amid the uncertainty that parliamentary elections will establish a U.S.-friendly government, the United States wants Pakistan to at least keep moving toward democracy — and Bhutto’s return could help that goal.

Musharraf had urged Bhutto to delay her return because of political uncertainty in Pakistan, including a pending court challenge to his presidential election victory this month.

The Supreme Court will rule soon on whether he was eligible to compete in the vote by lawmakers, since he also holds the post of army chief. If he is confirmed for a new five-year presidential term, Musharraf has promised to quit the military and restore civilian rule.

Bhutto said there was still a long way to go in political reconciliation with Musharraf, but added that she expected the court to decide in his favor. ”If the court did not stop his election, it’s unlikely to stop the result of that election,” she said.

After flying in, Bhutto declared she returned to fight for democracy and to help Pakistan shake off its reputation as a hotbed of international terrorism.

”That’s not the real image of Pakistan. The people that you see outside are the real image of Pakistan. These are the decent and hardworking middle-classes and working classes of Pakistan who want to be empowered so they can build a moderate, modern nation,” she said.

Bhutto became leader of the Pakistan People’s Party more than two decades ago after the military’s 1979 execution of its founder, her father Zulfiqar Ali Bhutto, a populist prime minister still exalted by many Pakistanis as the finest leader in the country’s 60-year history.

She served twice as the democratically elected prime minister between 1988 and 1996 — the first female premier in the Muslim world — but both governments fell amid allegations of corruption and misrule. After Musharraf seized power, she was charged with illegally amassing properties and bank accounts overseas while in office and she left Pakistan.

By Matthew Pennington. Associated Press writers Ashraf Khan in Karachi, Sadaqat Jan and Zarar Khan in Islamabad and Sarah DiLorenzo in New York contributed to this report.