The Tongan government says the fourth extension of the state of emergency is aimed at preventing any disturbances.
The emergency provisions, which were first put in place after the riots in Nuku'alofa last November, restrict civic rights.
Lopeti Senituli, who is a spokesman for the prime minister, Dr Feleti Sevele, says the privy council was acting on the advice of the Minister of Police that public order in Nuku'alofa continues to be seriously threatened.
"It's a precaution that has been taken by government to ensure that thetre is no further disturbances whilst the courts are hearing the cases arising out of the 16th of November."
Lopeti Senituli says the state of emergency will be reviewed after 30 days.
More than a 1,000 people have been arrested over the riots which destroyed much of the central Nuku'alofa.