ISLAMABAD, Pakistan — An Italian who survived an avalanche that killed fellow climbers on the world’s second-highest peak said today poor equipment and a mistake by a porter contributed to the tragedy.

Marco Confortola was among 30 mountaineers who began their ascent of K2 on Friday. He was stranded after an ice fall swept some climbers away and left others stranded in frigid conditions just below the 28,250-foot summit. In all, 11 people died.

Mr. Confortola said poor equipment — including ropes and spikes that broke — as well as sloppiness and inexperience were partly to blame for the disaster. A Dutch survivor, Wilco Van Rooijen, has said advance climbers laid ropes in some of the wrong places, including in a treacherous gully known as “The Bottleneck,” about 1,150 feet below the summit, where the avalanche later took place.

Mr. Confortola was rescued from K2 today and taken to a hospital with severe frostbite on his toes.

“What happened on K2 was the result of many things, one of which was bad luck,” he told Italian news agency ANSA. “There was also some sloppiness. A 656-foot rope, very light but strong … was not brought by a somewhat sloppy porter, which was just the beginning of the problems.”

K2 expeditions hire Pakistani tour operators who support them with porter services to carry gear to base camps and supply the camps.

Mr. Confortola blamed the first death of a Serbian climber on the equipment, ANSA said. The dead included three South Koreans, two Nepalis, two Pakistanis, and mountaineers from France, Ireland, and Norway as well.

Mr. Van Rooijen, who was rescued Monday, also blamed mistakes in preparation — not just the avalanche — for the loss of life. He said the advance climbers who laid ropes caused hours of delays, so some climbers reached the summit just before nightfall, while others turned back. Ice overhanging the route fell as the fastest mountaineers were descending some of the iciest and most difficult sections just below the summit.

Mr. Confortola said the expedition spent about an hour and a half under a huge block of ice overhanging the route “and it’s something you should not do at 8,400 meters (27,000 feet).”

In earlier interviews, he described how he and other climbers reached the summit late Friday and were stuck on the peak when disaster struck. As fellow climbers were swept away, he said he dug a seat in the snow and tried to survive with a friend Gerard whom he nicknamed Jesus. Gerard McDonnell, who died, became the first Irish person to reach the summit of K2.

Mr. Confortola said he heard a boom and witnessed a second avalanche. He saw two boots sticking out of a cascade of ice: “I recognized them, they were Jesus’.”

The Italian climber said he felt helpless when he and others made a futile attempt to rescue three Koreans dangling from a rope. He said he was too weak and had to give up when four Nepalese Sherpas came to help.

“I couldn’t take it anymore, I descended” alone, Mr. Confortola said. “The descent was devastating, especially the last part. But the worst moment was seeing the boots of Jesus, my friend.”

Mr. Confortola was the last survivor to reach safety. He limped into base camp with frostbitten feet yesterday, but thick clouds forced him to stay an extra night. Authorities took him to a military hospital where he was undergoing tests today.

“My toes are black, but I can still feel them, they’re painful,” Mr. Confortola was quoted as saying by the Apcom news agency on today. “Doctors are optimistic.” He said he wanted to go to Italy for treatment.

Government officials in Islamabad have promised to investigate the tragedy.

Shahzad Qaiser, at the Ministry of Tourism, which oversees tour companies that provide services to mountaineering expeditions, said he had not received a formal complaint against any tour operator.

Fatal accidents are common on the treacherous peaks that attract top mountaineers to Pakistan each summer, but this is the deadliest single incident in memory, surpassing the seven climbers killed on K2 during a fierce storm in 1995.

K2, which straddles Pakistan and China, is regarded by mountaineers as far more challenging than Mount Everest, the world’s highest peak. The mesmerizing giant pyramid of K2’s knife-edged ridges and icy slopes are steeper and prone to both avalanches and sudden and severe storms.

About 280 people have reached K2’s summit since 1954, when it was first achieved by Italians Achille Compagnoni and Lino Lacedelli. Dozens of deaths have been recorded since 1939.

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Associated Press reporter Marta Falconi contributed to this report from Rome.