Rescuers worked to clear a snow-blocked road and free 86 tourists, including 13 foreigners, stranded on Monday at the northern base camp of Mount Qomolangma in the Tibet autonomous region.

An "unexpected" snowfall delivered by Cyclone Phailin hit southwestern parts of Xigaze prefecture on Sunday, trapping tourists at the base camp.

Local authorities said many of the 13 foreigners were Japanese.

The base stands 5,200 meters above sea level, and the oxygen content of the air is about 40 percent of that at sea level, causing occasional cases of altitude sickness among visitors. So far, no casualties or injuries have been reported among the stranded tourists.

Snow continued to fall and hindered rescue operations on Monday afternoon, according to rescuers.

The average thickness of the snow was more than 45 cm, and drifts reached up to 60 cm at Rongbuk Monastery close to the base.

Weather forecasts predict continued cloud cover over the next three days, with temperatures remaining between -2 C and 14 C.

Mobile phone communications are working only intermittently, according to officials in Dingri county, Xigaze prefecture.

"Four vehicles are clearing the road. The trapped tourists have enough to eat and they remain emotionally stable," said Tian Shixin, a publicity official of the Xigaze government.

Tian added that officials of the autonomous region had activated emergency plans and three teams are leading the rescue operation.

By press time, the road to the Rongbuk Monastery has been cleared and some tourists had been rescued, according to a press release of the government of Tibet autonomous region.