A climber airlifted with altitude sickness near the peak of Japan's Mount Fuji last week returned to the slope and was rescued for a second time just four days later, authorities said Monday.

Officials urged people to be aware of the harsh conditions at the country's tallest peak during its off-season.

The climber was identified only as a 27-year-old Chinese student living in Japan. He made an emergency call on April 22 and was airlifted after developing symptoms of altitude sickness, police said, adding that his climbing irons also were damaged.

Last Saturday, he returned to the mountain's Fujinomiya trail about 3,000 metres above sea level to look for his cellphone and other belongings left behind, Shizuoka prefectural police said. Another climber found him there unable to move after he apparently developed altitude sickness for a second time, police said.

No penalty, even for off-season rescues

The mountain's hiking trails are officially open only from July to early September, but there is no penalty for hiking off-season. There also is no charge or penalty when a climber needs to be rescued, but the student's case prompted an uproar on social media and generated calls for him to be charged, at least for his second rescue.

The Shizuoka police urged all climbers to use caution, noting that the mountain has low temperatures and is covered in snow even in spring.

The 3,776-metre-high mountain was designated a UNESCO World Cultural Heritage site in 2013. A symbol of Japan, the mountain called "Fujisan" used to be a place of pilgrimage and is increasingly popular among hikers today.

To control overcrowding and risks from rushed overnight climbing through rocky slopes to see the sunrise, local authorities last year introduced an entry fee and cap on the number of entrants on the most popular trail and will introduce similar rules on other main trails this year.