A leading member of Tonga's pro-democracy movement, Akilisi Pohiva, is welcoming the appointment of Dr Fred Sevele as acting prime minister.
Mr Pohiva says it's an historic move because it's the first time a popularly-elected MP has been appointed to lead the government in the kingdom.
It follows the resignation of Prince 'Ulukalala Lavaka Ata from the post on the weekend.
Mr Pohiva says the Human Rights and Democracy movement will continue to talk to Dr Sevele, a current member, and keep on with its push for further changes in the kingdom.
"I will continue to discuss with him, the political reform process, together with other ministers and also together with the rest of the representatives of the people. I think we will have to work together, with him, until we see change in the very near future."
Our correspondent in Tonga says Dr Sevele is expected to be confirmed as the prime minister some time this week, by Crown Prince Tupouto'a, acting in his capacity as prince regent.
Meanwhile, the New Zealand Prime Minister, Helen Clark, has paid tribute to her outgoing counterpart in Tonga.
Ms Clark has sent her regards to Prince 'Ulukalala, with whom she's worked for six years...
I've met him on many occasions round the Pacific, the Pacific Islands Forum, and I wish him well for the future. This has come as quite a surprise to everyone in Tonga, and to ourselves. I look forward to meeting the acting prime minister. The fact that he is the acting prime minister indicates that this might not be a permanent state of affairs, but that's for the Tongan people to work out.