COLOMBO (AFP) - At least six people were killed and 10 others injured in Sri Lanka's capital on Friday (April 14) after a massive rubbish dump buried an estimated 40 homes during the traditional new year.

A 12-year-old boy and two teenaged girls died at the Colombo National hospital where 10 others were being treated after they were rescued, hospital spokeswoman Pushpa Soysa told AFP.

She said three other people who were pulled from the wreckage of homes were already dead by the time they arrived at the hospital on Friday night, raising the confirmed death toll to six.

Police said hundreds of troops had joined the search for survivors after the disaster at Kolonnawa on the northeastern edge of the capital.

President Maithripala Sirisena ordered troops and police to join firefighters in the rescue after the 91m-high dump caught fire and collapsed, officials said.

Police said the true scale of the damage remained unclear.

"A search for survivors is under way," the police said in a statement.

Dozens of homes collapsed after heavy rains overnight caused the garbage mountain to shift, officials said. It became further destabilised after a fire broke out, triggering landslides that buried dwellings.

Military spokesman Roshan Seneviratne said 100 soldiers were already digging through mounds of trash. Heavy earth moving equipment was also being deployed, he added.

Local residents said many people had left the area after the night's heavy rain.

"We think about 40 homes have been destroyed," a disaster management official told reporters.

Roughly 800 tonnes of solid waste is added daily to the open dump, angering residents who live nearby.

Sri Lanka's parliament was warned recently that the 23 million tonnes of garbage rotting at Kolonnawa was a serious health hazard.

Efforts are under way to build an electricity plant that could transform the solid waste into fuel.

Friday's fire broke out as the country marked its traditional Sinhala and Tamil New Year and most people were in their homes celebrating.