Military aircraft come to Nepal aid

Australian military aircraft could be in Nepal as early as Thursday to evacuate trekkers stranded after a huge earthquake.

Two RAAF C-17A Globemaster aircraft have departed for Nepal carrying 15 tonnes of supplies such as tarpaulins, blankets, water purification tablets and health supplies.

After unloading supplies they will take Australians to Bangkok.

Australian Defence Force chief of joint operations, Vice Admiral David Johnston, said the timing of the aircraft's arrival depended on getting access to Kathmandu airport, which is congested due to there being only nine parking spaces for aircraft.

"I'm hopeful that may be as early as Thursday but that is all about airport access," he told reporters in Canberra on Wednesday.

About 25 ADF personnel will remain in Nepal to support the aircraft, with teams of 10 providing medical support and security on board each of the Globemasters.

A Department of Foreign Affairs and Trade spokesman said about 1000 Australians had so far sought evacuation assistance.

The death toll from Saturday's devastating quake has now tipped 5000 people with about 8000 injured.

The country has declared three days of national mourning as the United Nations estimated eight million people had been affected.

Meanwhile, three Perth teenagers who were trekking in Nepal when the 7.8-magnitude earthquake struck have contacted their worried families.

Fremantle-based Rin Hutcheson and Jalada Wilson, both 18, and Raoul Poncin, 19, had not been heard from since last Tuesday when they were hiking in Lampang National Park.

Raoul's father Freddy Poncin posted on Facebook overnight that all three were safe but could not get out of the Langtang area.

"A very happy dad here!!!" he posted.

It is believed only one West Australian in Nepal has not made contact with family, Victoria Park university student Mitchell James Noga, 21, who is registered as missing on a Red Cross website.

Before the quake struck, he was in Pokhara, which was not as devastated as the capital Kathmandu.

He last made contact with his family 10 days ago.