The number of people killed in last week's devastating landslides and flash floods in Nepal and China has topped 1,000, according to authorities.

Nepal's National Disaster Risk Reduction and Management Authority says the death toll in the country now stands at 987, while Chinese authorities previously reported 16 deaths in Tibet.

More than 4,400 people remain missing as of Tuesday morning as rescue teams continue efforts to reach affected areas and locate survivors, CNN reports.

In Nepal, mass burials are taking place as communities deal with the scale of the disaster, while rescuers are still scrambling to reach around 900 workers believed to be trapped inside hydropower tunnels.

The disaster has devastated communities near Nepal's border with China, leaving homes, roads and infrastructure damaged or swept away by torrents of water and mud.