Sri Lanka's prime minister said the United Nations has arranged a worldwide public appeal to help the island nation's food, agriculture and heath sectors amid serious shortages caused by its worst economic crises in recent memory.

In his speech to Parliament, prime minister Ranil Wickremesinghe said the UN plans to provide £38.5 million in assistance over a four-month period.

Mr Wickremesinghe said that for the next three weeks it will be tough to obtain some essentials and urged people to be united and patient, to use the scarce supplies as carefully as possible and to avoid nonessential travel.

"Therefore, I urge all citizens to refrain from thinking about hoarding fuel and gas during this period. After those difficult three weeks, we will try to provide fuel and food without further disruptions. Negotiations are underway with various parties to ensure this happens," Mr Wickremesinghe said.

Sri Lanka is nearly bankrupt, having suspended repayment of its foreign loans. Its foreign reserves are almost spent, which has limited imports and caused serious shortages of essentials including food, medicine, fuel and cooking gas.

The island nation is due to repay £5.6 billion this year of the £20 billion in foreign loans it is scheduled to pay by 2026. Sri Lanka's total foreign debt is £40.9 billion.

Authorities have started discussions with the International Monetary Fund for a bailout package and Mr Wickremesinghe asked it to lead a conference to unite Sri Lanka's lending partners.

"Holding such a conference under the leadership of India, China and Japan will be a great strength to our country. China and Japan have different credit approaches. It is our hope that some consensus on lending approaches can be reached through such a conference," Mr Wickremesinghe said.

He said Sri Lanka will need £4.8 billion over the next six months to stay afloat.

A decision taken last year to ban agrochemicals and make the country's agriculture totally organic has halved rice production during the main cultivating season, though the ban has since been withdrawn. A lack of funds to buy fertiliser threatens future yields, too, causing fears of a food crisis.

It costs £481 million a year to import chemical fertiliser, Mr Wickremesinghe said.

"The task of rebuilding our declining agriculture must begin immediately. We are losing the international market for our export crops. Action must be taken to prevent this. Chemical fertilisers are needed to boost local agriculture," he said.

The economic crisis has led to political turmoil in the country with protesters camping out outside the president's office for more than 50 days calling for the resignation of Gotabaya Rajapaksa, who they accuse of being responsible for the crisis.