KABUL, Afghanistan (AP) – Campaigning for Afghanistan’s first direct presidential election ended with a burst of violence Wednesday as attackers set off a bomb in a failed effort to kill interim Afghan leader Hamid Karzai’s vice presidential running-mate.

Despite persistent violence, the United Nations declared this hard-luck nation ready for Saturday’s vote, a historic experiment with democracy after more than two decades of unrelenting ruin, from Soviet occupation to civil war to the repressive Taliban and the thunderous U.S. bombing campaign that ended their rule.

In a sign of the progress, Karzai and another top candidate held raucous, peaceful rallies at Kabul’s bullet-pocked sports stadium, once the scene of gruesome executions under the Taliban regime that was ousted at the end of 2001.

The bomb was detonated by remote control on a road in northeastern Badakhshan province when vice presidential hopeful Ahmed Zia Massood and other dignitaries were passing, presidential spokesman Khaleeq Ahmed said.

Massood – whose brother was assassinated by suspected al-Qaida agents in September 2001 – escaped unharmed, but one man was killed and five people were injured, including the former provincial governor, said the chief of the provincial criminal department, Fazel Ahmad Nazari.

Karzai, who called the attack “dastardly,” picked up three key endorsements as campaigning officially ended to allow two days of preparation for the election.

Two minor presidential hopefuls, ethnic Tajik former police officer Abdul Hasib Aryan and ethnic Pashtun Sayed Ishaq Gilani, dropped out and threw their support to Karzai, who is a Pashtun but has portrayed himself as someone who can unite this largely tribal society.

The president also got the endorsement of another Massood brother, Ambassador to Britain Ahmed Wali Massood, who leads the Nazat-e-Milli party of Karzai’s chief rival, former Interior Minister Yunus Qanooni. The ambassador said the entire party backed Karzai.

The U.S. Embassy warned of the threat of more attacks ahead of the vote.

“In the run-up to the Oct. 9 elections, potential continues to exist for demonstrations, riots, bombings and other violent actions against U.S. citizens and interests in Kabul and the rest of the country,” it said.

The area where Massood’s convoy was attacked is not considered a haven for Taliban rebels and had been relatively peaceful. It is, however, a center of Afghanistan’s booming opium and heroin trade, with countless poppy fields dotting the landscape.

Ahmed, the palace spokesman, would not comment on who might have been behind the assassination attempt, but he said violence would not derail Saturday’s vote.

“The elections will continue 100 percent. We knew from day one that as we got closer to the elections, the enemies of Afghanistan would try to disrupt them, but they will not succeed, ever,” he told The Associated Press.

U.N. Secretary-General Kofi Annan’s special representative for Afghanistan declared that as imperfect as conditions might be, the election would be fair enough to give Afghanistan’s leader legitimacy.

It is “with full knowledge of the difficulties that surround this exercise that we deem the degree of freedom and fairness adequate to allow the will of the Afghan people as a whole to translate at the polls, and the next president of Afghanistan to claim to represent the nation,” Jean Arnault said.

In the capital, Karzai addressed about 6,000 people at Kabul’s sports stadium, telling the crowd their vote would lay the foundation for democracy in the war-shattered nation.

One of his strongest rivals, ethnic Uzbek strongman Abdul Rashid Dostum, held his own rally at the stadium later in the day, mounting a brown horse – his electoral symbol – at the end as supporters pressed forward.

During Taliban rule, the concrete sports stadium was the preferred execution ground for criminals and others, and the public was encouraged to attend the bloody spectacles. Its transformation into a place of democratic rallies is a dramatic example of how far the nation has come.

But the stadium is still pocked with thousands of bullet holes from a quarter-century of war, particularly the internecine fighting that leveled much of Kabul in 1992-96, and it stands as one of countless examples of the nation’s destruction.

“I remember the Taliban used this very stadium to execute people, and now this is a place for entertainment and to hear our candidates speak,” said Abdul Habib, a 60-year-old mechanic who was in the crowd during Karzai’s speech.

Karzai urged the crowd to take part in the election, which pits 18 candidates.

“Your vote will elect a president for the next five years, but it will do much more than that as well,” he said. “By voting you are laying the first bricks in a wall of democracy that will last for decades and centuries in our country.”

Karzai is the overwhelming favorite, and he hopes a strong victory will add teeth to his often limited control of the vast, barren country. He has said his main goals are to carry on with reconstruction and to curb the power of warlords who still hold sway in much of Afghanistan.

A majority of votes must be won to avoid a runoff between the top two finishers.