The death toll from devastating flash floods in Nepal and Tibet has risen to at least 750, while more than 3,000 people remain missing as rescue teams race to find survivors and authorities warn of further flooding.

Axar.az reports, citing The Guardian, that Chinese authorities on Sunday reported 16 deaths and 546 people missing in Tibet, including 261 foreign nationals. Nepali officials reported 734 deaths and 2,498 people missing.

According to China's state broadcaster, the missing foreign nationals include 104 Nepali citizens, 49 Indians, 33 Latvians, 18 Americans and 15 British nationals.

More than 3,700 people have so far been rescued in Nepal.

In a major breakthrough late Saturday, the Nepali army managed to insert a pipe into a tunnel at the Trishuli 3A hydroelectric project, where workers are believed to be trapped.

“We have already started sending air through the small opening, and we will now begin excavation work and send the rescue team inside,” Home Minister Sudan Gurung said.

More than 100 workers may still be trapped inside tunnels at the Trishuli 3A and 3B hydropower sites, with rescue teams focusing their efforts on reaching them.

Nepal's National Disaster Risk Reduction and Management Authority warned Sunday that water levels were rising in the Bhotekoshi River in Rasuwa and urged rescue teams to exercise caution.

The floods have also raised fears of further disasters after torrents of ice and mud created large lakes in several areas. One newly formed lake has become a potential source of additional flooding.

Chinese and Nepali foreign ministers spoke on Saturday and discussed sharing satellite and hydrological data. In Tibet's worst-hit area of Gyirong, rescue operations were temporarily suspended because of the risk of further flooding from a newly formed lake.