"As Papua New Guinea is a Christian country, the government has recognised the need to pray together as a nation," Prime Minister Peter O'Neill said.
"Therefore, [the] National Executive Council has approved for two days in the year to be national days for prayer and fasting.
"The first of these two days, the National Covenant Day, falls this Sunday. Therefore, Monday, the 27th of August, has been declared a public holiday throughout PNG.
"All employers and employees in the public and private sector are required to allow their staff to commemorate this day," he said.
Business chambers have already criticised the lack of notice and the inconvenience caused.