The Tongan government says worries that some of the groups pushing for political reform could spark renewed violence prompted the latest extension of the state of emergency in parts of the capital Nuku'Alofa.
The state of emergency was first proclaimed immediately after the riot of November 16th last year.
It has been extended for another 30 days - the tenth such extension since the riot.
The Information Minister, Afu'alo Matoto, says despite a commitment by the government to political reform the police chief is concerned that some elements within the pro-democracy movement pose a threat to public order.
"There are different versions of political reform and it's these different factions that are of concern as far as the Minister of Police is concerned that could easily cause some eruption and cause some disturbance."