KATHMANDU (AFP) - Two Nepali sherpa guides have died of suspected altitude sickness in the Himalayas, a tour operator said Wednesday.

The guides were assisting an 11-member team on the 8,481m-tall Makalu peak, the fifth-highest mountain in the world.

Mr Parsuram Karki of the Thamserku Expedition tour agency said the two men had complained of altitude sickness on Tuesday night at Camp II, located at 6,700m, but died as their team members were taking them down.

"Their bodies have been brought to the base camp," Mr Karki told AFP.

Altitude sickness strikes when people ascend heights too quickly, with the decreased atmosphere pressure causing headaches, fatigue and dizziness.

In separate incidents, two trekkers - one Japanese and the other South Korean - died of altitude sickness last month while on their way down from Nepal's Everest base camp.

Every year hundreds of people from around the world travel to the Himalayas in Nepal for the brief spring climbing season, when conditions are at their best.

Mountaineering is a major revenue-earner for impoverished Nepal, home to eight of the world's 14 peaks over 8,000m.