Altitude sickness poses the biggest challenge for rescuers from the military and armed police in their quake-relief efforts in northwest China's Qinghai Province, a senior military officer said Tuesday.

Wang Zhenguo, an officer with the Yushu quake-relief headquarters of the Chinese People's Liberation Army (PLA) and armed police, said at a press conference that no casualty had been reported among the quake-relief soldiers and armed police so far despite the difficulties.

However, all quake-relief soldiers and armed police suffered altitude sickness including dizziness, short of breath, fatigue and coma, said Wang.

Two soldiers had pulmonary edema after catching colds and were being treated in hospital, he said.

But the majority of the quake-relief soldiers only had slight symptoms such as dizziness and short of breath as most of them were young and had previously participated in military tasks on plateaus, according to officers attending the press conference.

To cope with altitude sickness, most of the soldiers were told to carry more medicine as well as oxygen concentrators and tanks, Xie Weikuan, an officer with the PLA General Logistics Department, said at the same press conference.

As of Tuesday, the PLA General Logistics Department had supplied 5,000 portions of medicine, 100 oxygen concentrators and 145 oxygen tanks to help soldiers cope with altitude sickness, Xie said.

A team of 15 medical experts were sent to the quake zone on April 15. They had bought with them more than 10,000 pamphlets on the prevention of altitude diseases and were providing medical help and educating people about altitude sickness, he said.

Soldiers from the PLA and armed police have rescued more than 1,560 people and given medical aid to more than 20,000 injured in the quake zone as of Monday, said Huang Xueping, spokesman with the Ministry of National Defense, at the same press conference.

Huang said that nearly 12,800 soldiers and armed police had been sent to the quake zone to help with disaster relief as of Monday.

Thirteen medical teams and 89 quake-relief aircraft from the PLA and armed police had been dispatched to the quake zone, he said, adding rescuers from the military and armed police had also transported 5,200 tonnes of tents, food and other relief material.