The International Labour Organisation is sending a delegation to Fiji after the military government last week introduced a new decree, which unions say threatens their freedom.
ILO Director General Juan Somavia has expressed serious concern about the law, which the government says is aimed at protecting essential national industries, like its airline.
Two trade unionists, including Fiji Trades Union Congress president Daniel Urai, were also arrested last week.
In a statement, Mr Somavia says the delegation is being sent because of the grave situation in Fiji and the fear it could deteriorate further.
Mr Somavia says he wants to find out how the ILO can help all parties involved.