Nepal observed a national day of mourning on Monday, the 13th day since catastrophic floods struck the Himalayan border region with China's Tibet, killing at least 1,380 people and leaving more than 5,500 missing.

Government offices across Nepal and diplomatic missions abroad flew the national flag at half-mast, the Ministry of Home Affairs said in a statement.

The date marks the final day of the traditional Hindu mourning period, during which close family members remain at home and relatives visit to pay their respects. Rituals are held on the final day to pray for those who died.

No wider government events were planned, as search and rescue operations remain ongoing and resources are limited.

"There are no government programmes organised as the rescue and search operation is still going on in the flood-hit areas," said Phanindra Paudel of the National Emergency Operation Center.

The disaster was triggered on August 26 when a glacier broke off and sent a massive wall of mud and rock crashing into a river along the Nepal-Tibet border, causing catastrophic flooding along the Bhotekoshi River.

In recent days, rescuers pulled four survivors from the debris. A Chinese national was extracted from a tunnel at a hydropower site on Saturday. Two hydropower workers were rescued from a separate tunnel on Friday, and a Nepali woman was pulled from her buried home on Saturday.

Rescue efforts have focused on 12 hydropower projects where approximately 900 workers are missing. Authorities believe around 500 are trapped in various tunnels. Specialised teams from India, China, South Korea and the United States have been searching through debris, damaged structures and tunnels at the sites.

President Ram Chandra Paudel, the ceremonial head of state, was touring flood-hit areas on Monday to survey the damage, his aide said.

In Kathmandu, family members of missing workers gathered near the offices of the prime minister and key ministries to demand faster search efforts.

Sumana Shrestha stood with relatives holding a poster bearing a photograph of her 55-year-old husband, a consulting geologist who has not been heard from since the day of the flood. He had been due to return home after his shift at the project office for the Trishuli hydropower plant, a two-and-a-half-storey building that was buried by debris.

"We are here because we have not heard of any rescue attempt on this project, but it has been 13 days already," she said. "The only thing we have been able to do is pray to God and hope for a miracle."

Another protester, Mahesh Prasad Shrestha, held a photograph of his brother Niraj Shrestha, a 52-year-old engineer who worked at the same site. He said authorities sent only a small excavator by helicopter on the sixth or seventh day after the disaster.

"They should have ordered big helicopters from places like China or India to fly in equipment," he said.