Chinese rescue team members discuss their plan of action in Kathmandu on Tuesday. Photo: Cui Meng/GT

 Relief workers face huge challenges in reaching the remote mountain areas worst hit by the earthquake in Nepal, with heavy rains exacerbating the problems, the UN said on Tuesday, four days after a monster earthquake killed more than 5,000 people.

As the Himalayan nation's Prime Minister Sushil Koirala said getting help to remote areas was a "major challenge," aid finally began reaching areas that have had to fend for themselves since Saturday's 7.8-magnitude quake. The official toll in Nepal alone stood at 5,057 as of press time, while more than 100 people died in neighboring countries such as India and China.

Sushil Koirala said the government is doing all it could but is "overwhelmed."

The UN has estimated that 8 million people have been affected - more than a quarter of the country's population. Foreign aid is slowly trickling in but is being hampered by congestion at Kathmandu's sole airport.

China is trying to bring more of its own citizens home from Nepal as rescue work enters its third day, the Chinese authorities said on Tuesday.

A total of 1,799 Chinese citizens stranded in Nepal following the earthquake had been brought home by Monday night, according to the China National Tourism Administration. Most were in the country on vacation. There are 12 flights planned between China and Nepal on Tuesday, flying to Kathmandu from the cities of Chengdu, Kunming, Guangzhou and Lhasa. Three cargo aircraft will also fly to Nepal from Beijing to conduct relief missions.

On Monday alone, four Chinese airlines repatriated 776 Chinese citizens with 14 planes flying between Nepal and China.

Following the earthquake, a 62-strong Chinese search and rescue team, plus six dogs, was sent to Nepal's capital Kathmandu, according to the China Earthquake Administration. Their plane was loaded with 20.5 tons of relief materials.

Qu Guosheng, deputy director of the team, told the Global Times in Kathmandu Tuesday that parts of the city alongside the Bishnumati River and the nearby village of Balaju have been most affected. The foundations of houses along the riverbank have been slowly eroded by the water, making the houses more vulnerable to tremors, Qu said.

The Global Times reporter Tuesday followed the rescue team to quake-affected areas alongside the river and to the mountainous areas in southwestern Kathmandu. The situation was relatively better here than in Balaju. There were no landslides here, despite the heavy rain. The team visited every house in the area to see if anyone was trapped inside. If there were people stuck under rubble they attempted to release them, if no one was trapped then the team recorded the house's location and passed the information on to the authorities.

The Chinese government will provide 20 million yuan ($3.3 million) in humanitarian aid to Nepal, the Ministry of Commerce said on Sunday, including tents, blankets and generators.

Agencies contributed to this story