A 13-year-old American boy on Saturday became the youngest ever climber to conquer Mount Everest, the world's highest mountain, a climbing website said.

Jordan Romero from Big Bear, California, scaled the 8,850 metre (29,035 feet) summit from the Tibetan side, on the same day a Nepali man broke his own world record for the most number of successful Everest attempts.

The ascent has put Romero one step closer to reaching his goal of climbing the highest mountains on all seven continents.

"It is just a goal," Romero had said in the Nepali capital Kathmandu in April. He has already climbed five peaks including Mount Kilimanjaro in Africa, and needs to climb the highest peak in Antarctica.

The previous youngest person to summit Everest was 16-year-old Temba Tsheri Sherpa of Nepal.

Romero was accompanied by a team including his father Paul, a critical care paramedic, and Sherpa guides. He said his aim was to pick a small piece of rock from the top of the world as a memento and wear it in a necklace.

His next mission is to climb the highest mountains in all 50 states in the United States.

More than 4,000 climbers have reached the top of Mount Everest since it was first climbed by New Zealander Sir Edmund Hillary and Nepal's Tenzing Norgay Sherpa in 1953.

On the same day as Romero, Nepali mountaineer Apa Sherpa broke his own record and climbed Mount Everest for the 20th time, said Ang Tshering Sherpa, chief of the Asian Trekking Agency.

Apa, 50, who lives in the United States, reached the summit on Saturday along the Southeast Ridge route. He carried a banner all the way to the summit to raise awareness of the environmental impact of climate change on the Himalayas.

"It is a fantastic achievement by one individual," said Elizabeth Hawley, who chronicles major climbs in the Himalayan mountain range. "Going back year after year after year and succeeding each time is really amazing."