Rescuers on Monday spotted the body of an Indian climber on Mt. Everest, raising the confirmed death toll during the busiest mountaineering season to six, local officials said.

Ravi Kumar, 26, from Uttar Pradesh, had been missing since Saturday after making it to the top of the world's highest mountain. Earlier Monday two other climbers -- a Slovak and an Australian -- were reported to have died Sunday, raising to three the number of climbers who died at a time when more than 100 people were attempting the death-defying final stage to the peak.

Kumar's body was found just below what is popularly known as the balcony of the mountain. He made it to the top at 1:28 p.m., but by nightfall had not arrived at Camp 4 where most climbers stay the night.

"It was a late summit. Usually climbers summit the mountain in the early morning and have ample time to return to Camp 4," said Thupden Sherpa, manager of Arun Treks and Expedition, Kumar's expedition organizer.

Camp 4 is located at 7,950 meters. Slopes above it constitute the so-called death zone because of the extreme temperatures and high winds there.

"Sherpas who went searching for Kumar spotted his body today at an altitude of around 7,800 meters. Kumar apparently fell while descending," said Hemant Dhakal, an official at Nepal's tourism ministry.

The Sherpas were unable to retrieve his body, which is lying 200 meters below the route of descent.

Vladimir Strba, 48, who stood atop the 8,848-meter summit Sunday morning, fell ill while descending and died at Camp 4 at 4:45 p.m. that day, his expedition organizer Sudin Thakuri of Kathmandu-based Utmost Adventure Trekking told Kyodo News.

"He was frost-bitten and looked very weak. Sherpas helped him to Camp 4, but couldn't save him," Thakuri said of Strba, who was climbing without supplementary oxygen.

From the Tibet side of the mountain, Francesco Enrico Marchetti, a 54-year-old Australian, died on Sunday, apparently after suffering from altitude sickness, according to Nabin Trital, who arranged the logistics for Marchetti's expedition.

"While climbing up, Marchetti fell ill at 8,300 meters after which his health swiftly deteriorated. He passed away at 8,000 meters while descending to lower altitude," Trital told Kyodo News.

Roland Yearwood, 50, an American doctor from the Georgiana Medical Center in Alabama, also died Sunday at an altitude of 8,400 meters, according to Murari Sharma, who runs the Everest Pariwar Expedition, local organizer of Yearwood's expedition.

"It is unclear what caused his death and whether he died while descending after standing atop the mountain or while pushing for the summit," Sharma said.

Yearwood was part of a 16-member group led by Dan Mazur, an experienced American-British mountaineer.

Those four deaths over recent days raised to six the number of climbers who have died while climbing Mt. Everest this season, the busiest ever.

Last month, famed Swiss alpinist Ueli Steck, 40, died in a climbing accident, and Nepali mountaineer Min Bahadur Shercha, 85, died of apparent heart attack while attempting to become the oldest person to climb the mountain.

More than 370 climbers have been issued permits to climb Mt. Everest from the Nepal side this season, an all-time record.

Spring is the most popular season for climbing the mountain because of favorable weather. Climbers leave for the mountain in April to acclimatize and wait for a few favorable weather periods that usually appear from mid-May to late-May.

Nepal's mountaineering industry was devastated by natural disasters in 2014, when an avalanche killed 16 Nepali rope-fixers on Mt. Everest, and in 2015 when a quake-triggered avalanche on the mountain left 18 people dead.

A "summit wave" of climbers is expected to head for the top of Mt. Everest on Monday. Gyanendra Shrestha, a tourism ministry official, told Kyodo News by phone from the mountain's Base Camp that "between 100 and 150 climbers are trying to stand atop the mountain today."