A police round-up of opposition leaders and union officials in Fiji is being described as political persecution.
The leaders of the two opposition parties, the general secretary of the Council of Trade Unions, and two others have been held in custody in Suva overnight.
Police were due to resume questioning the men today, about a meeting organised by an NGO last week to discuss the 2013 constitution.
The gathering was held without a government permit.
Those arrested included the leaders of the National Federation Party and Sodelpa, Biman Prasad and Sitiveni Rabuka, and National Council of Trade Unions general secretary Attar Singh.
Academic Tupeni Baba and NGO leader Jone Dakuvula were also taken into custody.
Attar Singh's lawyer said none of the men had been charged yet.
Police also searched the homes of Mr Singh and Mr Prasad, as well as the National Federation Party headquarters, where a laptop was seized.
Amnesty International has called for the men's immediate release.
Amnesty South East Asia and Pacific director Rafend Djamin said there was no reason to suggest the meeting to discuss the constitution posed a threat to national security.
"This is a brazen crackdown on people for peacefully exercising their right to freedom of expression," Mr Djamin said.
"Fijians should be free to openly discuss their supreme law and even criticise, without fear of reprisals."
An opposition MP, Prem Singh, said people had a right to discuss the constitution and the police were being heavy-handed.
"This is totally unwarranted because it was a private meeting, and all the candidates who were part of the dicussions and the debate were there on the invitation of the NGO."
The arrests undermined the country's democracy and freedom of assembly, Mr Singh said.
A spokesperson for New Zealand's Foreign Affairs Minister Murray McCully - who was at the Pacific Island Forum being held in the Federated States of Micronesia - said the government would be concerned about any action that undermined democratic principles in Fiji.
The Ministry was seeking information on the circumstances of the reported arrests of opposition politicians in Fiji, and clarification on the status of those reportedly arrested, the spokesperson said.