At least one Australian has been reportedly killed in an avalanche at Mount Everest, triggered by the deadly earthquake that rocked Nepal on Saturday.
An expedition leader for the Dreamers' Destination Treks and Expeditions tour company told reporters he had lost four members of his group, including an Australian.
"I have lost four team members in the avalanche – two Nepalese, one Chinese and Australian," said Temba Tsheri Sherpa. "But the situation is so bad, this is only the beginning of bad news."
Foreign Minister Julie Bishop said she was aware of the report an Australian had died on the mountain and the "Australian embassy in Kathmandu is urgently seeking to confirm those reports".
She said the safety of more than 830 Australians had been confirmed but did not say how many were still unaccounted for.
Prime Minister Tony Abbott has reassured family members of missing Australians in Nepal that they should not "assume the worst" after the deadly earthquake and aftershocks struck the region, killing more than 3200 people.
On Sunday, the Department of Foreign Affairs and Trade said almost 350 Australians are unaccounted for in the region, with the Australian embassy in Nepal able to get in contact with 200 of the 549 registered Australian travellers in the area.
Mr Abbott said information was coming in slowly from remote parts of what is a remote country. Australia has allocated $5 million in aid so far and "will consider what further response, what on-the-ground response we might be able to make in the next day or so."
"Australians do go trekking in that part of the world and because someone is trekking in that part of the world we shouldn't assume the worst," Mr Abbott said.
"Yes, there are Australians who are unaccounted for, and people whose family members, friends or loved ones are known to be in Nepal and northern India should at first do their best to make contact with them.
"A lot of people who are out trekking are not easy to contact. But if they can't make contact then obviously it's important to be in contact with the Department of Foreign Affairs [consular line]."
Foreign minister Julie Bishop said damage to infrastructure had made communication difficult but she also urged families to try to contact their loved ones directly.
One of those missing is aid worker James Brinson, an engineer whose parents live in south Sydney. The 27-year-old was volunteering for World Vision in Dhaka to provide water and sanitation, his father Ivor said, but he was trekking at Goecha La near the border of Nepal and India as part of a three-week holiday when the earthquake struck.
"I think he'll be alright, because he's a fair way away from Kathmandu," Mr Brinson said. He didn't expect any news for at least four days.
"He left from a village. . .on Tuesday for an eight-day trek, so that means he's probably up at the pass now. Hopefully he'll be safe up there.
"I wasn't too worried, but it's still worrying when you can't get into contact with people."
On Sunday, Canberra man William Sargent phoned multiple hotels in Nepal in search of his 19-year-old son Alan, who was in Chitwan National Park when the earthquake struck. At 6pm, he had good news: a phone call from Alan to say he and his travelling partner were safe and well.
The number of Australians reported as missing by relatives on The Red Cross's Family Links website fluctuated on Sunday.
Among those listed are Zachary Sheridan, the younger brother of Packed to the Rafters star Hugh Sheridan, who last contacted his family on April 22 near Mount Everest; Matthew Graves, who posted pictures of temples to Facebook shortly before the earthquake; and Brisbane man Adam Jay Murphy, 27, who was in Pokhara, several hours west of Kathmandu.
Toni Louise Perry, 37, left for Everest base camp on Friday and was likely in the lower hills when the earthquake hit, her close friend Fiona McCuig said.
"We are hoping that she would be safer in the hills than in Kathmandu," she said.
Chatswood woman Isabel Baudish, 25, was trekking the Annapurna Circuit with a friend, after doing some volunteer work in India. Her father Peter said he was concerned about his daughter but understood that phone and email contact would be difficult.
Victorian reserve grade football player Richard Jaroszczuk, 22, is listed as missing from base camp at Mount Everest, while Brisbane friends Ben Flanders and Jai Williams have not made contact after planning to climb to the Mt Everest base camp.
Mr Flanders's mother Trish said he left Australia two weeks ago, with the intention of going on a three-week trip with friends.
She said her 25-year-old son Ben, a twin, was physically strong but had embarked on the trip despite recovering from serious chest injuries.
"If I wasn't a spiritual person, I would be frantic….But I'm not crying at the moment and maybe that means he may be alright," Ms Flanders said.
Australia offers assistance
An Australian Crisis Response Team will travel to Nepal as soon as possible to help establish the welfare of the missing Australians. Two humanitarian experts will also be deployed.
Australia will offer $5 million in aid, including $2.5 million to assist Australian non-government organisations, $2 million to support United Nations partners; and $500,000 to support the Australian Red Cross.
Red Cross International spokesman, Mark South, who is based in Kathmandu, said there was a significant need for medical supplies in the country because the hospitals were stretched for the massive numbers of injured.
Shelter was also pressing issue as the damage had forced thousands of people in the city to camp under tarpaulin and tents. Monsoon conditions were due in about six weeks, he said, and could pose a major threat if large numbers of people were still camping out.
Access to food and water was also an immediate concern, with any road blockages putting huge pressures on the delivery of goods and fuel to the city and limiting the ability of rescue worker to get to more remote areas.
"Pretty much everything into Nepal comes through India. So if the roads are blocked, which they are likely to be at the moment, then that can be a major issue if goods can't get into the city or can only come by plane," Mr South said.
with Nick Miller, Angelo Risso, Tom Arup
If you are concerned for a relative or friend in Nepal, call the Department of Foreign Affairs and Trade 24-hour consular emergency line on 1300 555 135 within Australia or +61 2 6261 3305 from outside.
