"The National Disaster Management Center reports that at least six people have died, 300 people are missing and 150 houses are destroyed," Xinhua quoted the spokesman as saying at a daily news briefing here.
"OCHA is in close contact with this centre and stands ready to support as requested," the spokesman added.
"The Sri Lankan Red Cross Society has mobilised first aid teams, while the World Health Organization (WHO) is supporting the Sri Lankan Ministry of Health's efforts to assist the affected communities," he noted.
The landslide hit a village in the hilly area after days of heavy monsoon rains. More than 100 people are believed to have been killed Wednesday as it buried scores of houses, and the toll is likely to rise, reports said.
The commander of Security Forces Headquarters, Maj. Gen. Mano Perera, said that the security forces took part in a massive rescue operation. Some houses were buried in more than 30 feet of mud following heavy rains in the area the previous night.