Dry weather has gripped much of PNG in recent months, while frosts in the last fortnight in the country's highland regions have destroyed vital food supplies, the government said late on Monday.

The El Nino is typically linked to dryness and frosts are often an early symptom of the phenomenon, weather experts say.

Prime Minister Peter O'Neill warned of an escalation of unfavourable conditions across the rest of Papua New Guinea as the El Nino strengthens over the next few months. “This drought has the potential to be worse than 1997 and 1998."

A state of emergency has already been declared in Enga and Southern highlands provinces in Papua New Guinea.

The highland provinces of Papua New Guinea are a key coffee producing region, one of the country's few commodities that are exported. Papua New Guinea accounts for approximately 1 percent of global coffee supplies, the World Bank Estimates.

Aid workers said it was too early to assess the damage to the country's coffee industry, but added that Papua New Guinea would face a potential humanitarian emergency if O'Neil's assessment comes to pass.

"Everyone has their own garden and they rely very heavily on it for food. If their gardens are destroyed by frost or it becomes very dry because of a lack of water then there could be a significant proportion of the population in food stress," said Blossum Gilmour, CARE Papua New Guinea's assistant country director.

Papua New Guinea's agricultural sector accounts for approximately 25 percent of the country's gross domestic product, PricewaterhouseCoopers estimates.

Reporting by Colin Packham; Editing by Michael Perry and Himani Sarkar, via the Thomson Reuters Foundation