Officials from China's Tibet Autonomous Region said at a press conference that the highest number of missing foreigners was from Nepal at 104, while 49 Indian, 33 Latvian, 18 US and 15 British citizens were also unaccounted for.
Authorities in Beijing have notified foreign missions.
The nationality breakdown was the first from the Chinese side since the collapse of a glacier on Wednesday unleashed a torrent of ice, rock, mud and debris down Himalayan rivers.
Authorities said 16 people had died in Gyirong County as of Saturday evening and that 546 were missing.
In Nepal, the disaster authority said at least 734 people were killed on its side of the border, 2498 are missing, among them at least 540 foreigners, including 42 Australians, while 7514 have been rescued.
Local police told Reuters that residents and rescue workers have moved to higher ground after the water level in the nearby Trishuli River rose over the past few hours, underscoring the risk of further flooding even as rescue efforts continue.
The disaster was "caused by glacier instability under the long-term effects of global warming", Chinese state broadcaster CCTV reported on Sunday, saying it is a "new and prominent feature of cryosphere disasters" on the Tibetan plateau.
It took six to seven minutes for the mudslide from the Nepalese side to reach the Gyirong border crossing, CCTV reported, citing the findings of Chinese scientists.
Surveillance footage from the crossing showed torrents of water and debris engulfing buildings while people tried to flee.
China's Foreign Minister Wang Yi told his Nepalese counterpart in a Saturday telephone call that the mudslide was their "most severe cross-border disaster" in recent years, and that rescue operations were of unprecedented difficulty and complexity, CCTV reported.
China has mobilised over 2100 emergency rescue workers and allocated at least 220 million yuan ($A45.5 million) to support relief efforts. It is also providing emergency cash aid, disaster relief supplies, satellite and hydrological data and tunnel rescue experts to Nepal, the state broadcaster said.
The countries are working together to identify missing citizens and foreign nationals, as well as strengthening cooperation in disaster prevention and mitigation, and climate-change response, CCTV reported.
Nepal's Finance Minister Swarnim Wagle told Reuters the government's initial estimate was that rebuilding would cost between $US4 billion ($A5.6 billion) and $US5 billion ($A7 billion).
"This is just an estimate. Loss and damage is being assessed," he said.
Foreign Minister Shisir Khanal said Nepal required specialist assistance to rescue people trapped in tunnels; restore transport and communication lines where bridges had been destroyed; identify bodies; conduct DNA testing; and store bodies for longer periods.
A team of Indian tunnel experts arrived in Nepal on Saturday, he said, while China's Xinhua news agency reported Beijing had dispatched five tunnel experts to support rescue efforts, with four more due to join them.
India has already sent three flights carrying 60 tonnes of relief supplies, including blankets, medicines, and food.
More than 90,000 people are likely to have been affected by the disaster, the Red Cross estimated.
with AP
