KATHMANDU (AFP) -- Rescuers in Nepal were battling hostile terrain and bad weather Tuesday to recover the bodies of 24 people, including a government minister and top conservationists, killed in a weekend helicopter crash, officials said.

The Russian-made helicopter chartered by the World Wildlife Fund crashed on Saturday soon after taking-off from Ghunsa in the remote mountainous east of the Himalayan kingdom.

"Due to the rugged terrain the rescuers have to use ropes to access the crash site and recover remains. This is why it is taking a long time," Nepal's civil aviation authority said in a statement.

Rescuers had searched for two days before finding the downed chopper and no survivors.

On board were Nepalese Forest Minister Gopal Rai, the Finnish embassy's charge d'affaires Pauli Mustonen, senior World Wildlife Fund officials from Australia, Britain, Canada and the United States, and Margaret Alexander, deputy director in Nepal of the US government's international aid arm, USAID.

Nepal's government has declared that Wednesday will be a public holiday and a day of national mourning.

"The national flag at all government offices will be flown at half-mast," government spokesman Dilendra Prasad Badu told AFP.

"The government expresses its heartfelt condolences to families of the deceased," he said. Matthew Kahane, Nepal's United Nations representative, described the deaths in the crash as a "terrible loss for the country and the international community."

Remains of the victims were scattered over a wide area and were not immediately identifiable, as the helicopter appeared to have caught fire after crashing, the civil aviation authority said.

It said dozens of people were working in rain and mist to assist in the recovery operation.

"At least 30 police, soldiers, locals and mountaineers are at the crash site retrieving the remains, but aerial evacuation has been prevented by bad weather," said Purshottam Shakya, a recovery coordinator at Kathmandu's Tribhuvan Airport.

"We will bring the bodies to Kathmandu as soon as the weather allows," Shakya said.

A temporary helipad has been set up some 3.5 kilometres (two miles) from the crash site.

Nepal's government has formed a seven-member team to investigate the crash, one of the worst in its aviation history.