American mountaineer Anna Gutu and a Nepalese guide Mingmar Sherpa were confirmed Sunday dead after avalanches struck the slopes of a Tibetan mountain, while two others remained missing, according to tour companies and Chinese media reports.

Mount Shishapangma, one of the highest mountains in the world, peaks at 26,335 feet above sea level and is entirely located within Chinese territory.

The accident occurred Saturday afternoon "at an altitude of between 7,600 and 8,000 meters", China's state news agency Xinhua said, citing the Tibet Sports Bureau, which confirmed the toll.

Mingma David Sherpa of Elite Exped, which was handling the expedition, told AFP that Anna Gutu, an American mountaineer, had been killed.

"We have received reports that Anna and her guide were hit by the avalanche yesterday, their bodies have been recovered," he said.

"There are other climbers missing as well and rescue efforts are underway," he said.

Those efforts were complicated by the fact that "helicopters cannot be used" on the mountain due to Chinese restrictions, he added.

Tashi Sherpa of Seven Summit Treks identified the missing as American climber Gina Marie Rzucidlo and her guide Tenjin "Lama" Sherpa.

"Two avalanches hit the mountain yesterday, impacting several climbers. Some were injured and two, American climber (Gina Marie Rzucidlo) and our guide Tenjin, are missing," he said.

"Search efforts are underway."

The avalanches also seriously injured Nepalese mountain guide Karma Geljen Sherpa, who was escorted down the mountain by rescuers and is currently in stable condition, according to state-owned Xinhua News Agency.

A total of 52 climbers from various countries including the U.S., Britain, Japan, and Italy were attempting to summit the mountain when the avalanches hit, Xinhua said.

All mountaineering activities have been suspended on Mount Shishapangma, Xinhua said.

Tenjin became the toast of the mountaineering community this year after setting the record for the fastest summit of all 14 of the world's 26,000-foot mountains alongside Norway's Kristin Harila.

The pair finished the feat in 92 days when they reached the peak of Pakistan's K2 in July.

A statement posted on Harila's Instagram said she was headed to Nepal to "help in any way she can."

"Our thoughts and prayers are with Lama and his family," it added.

The two women on Shishapangma were in a race to become the first American woman to summit all 14 peaks, according to Nepali newspaper The Himalayan Times.

Gutu had been chronicling her mountaineering feats on Instagram. Last month, she wrote that she had made it to the summit of Dhaulagiri and also posted dramatic video of her making it to the summit of Manaslu.

In a June Instagram post, Gutu wrote that she had summited Mount Kanchenjunga 

"I became another step closer to my big dream," she wrote next to a photo of her atop the summit.

The Associated Press contributed to this report.

In:
• Tibet
• Obituary