At least 150 people are now known to have died in eastern Papua New Guinea in floods triggered by heavy rain, reports from the Pacific nation say.
Hundreds of people have been displaced, officials say, and a state of emergency has been declared in the affected area.
Roads and communications in the region have been badly damaged, hindering the relief effort.
Aid is starting to arrive but health officials say they are concerned about a lack of food and spread of disease.
The flooding occurred after Tropical Cyclone Guba brought severe weather to the region.
Police spokesman David Terry described the situation in worst-hit Oro Province as "very sad" and said he expected the death toll to rise.
"We need a massive relief effort to stop people starving," he told Reuters news agency.
Helicopters began ferrying in aid from the capital, Port Moresby, on Wednesday.
People have been flocking to Oro's provincial capital, Popondetta, in search of food and water, local daily The National said, and officials fear others could be stranded in remote areas.
The Australian government has said it "stands ready to assist" Papua New Guinea if asked.