Half the candidates contesting East Timor's presidential vote next Monday have complained that attempts are being made to manipulate the poll process.
Monday's election is crucial for the fledgling state
In a joint statement, they alleged the ruling party had received preferential treatment for its election observers.
The four also complained of threats of violence and intimidation and asked the UN to guarantee security for the vote.
At least 32 people were hurt in clashes this week. The election body has said everything would be ready for the poll.
Call for restraint
Candidate Joao Viegas Carrascalao read the statement at a press conference joined by Fernando "Lasama" de Araujo - chairman of the opposition Democrat Party - Lucia Lobato and Francisco Xavier do Amaral.
"There's been a lot of intimidation, a lot of violence, and a lot of threats. We fear that violence can occur on the day of the vote," they said.
They said they had been unable to prepare proper voting checks as their election observers had only just received their identity cards ahead of Monday's poll.
PM Jose Ramos-Horta is one of eight candidates
But observers for the ruling Fretilin party said had received their compulsory papers well in advance, they said.
Eight contenders are standing in the fledgling nation's first presidential election since gaining independence from Indonesia in 2002.
Other candidates include current prime minister and Nobel Peace Prize winner Jose Ramos-Horta and the Fretilin chairman, Francisco Guterres.
Separately, Mr Ramos-Horta and Fretilin officials accused a member of the National Election Commission of interfering in the poll by backing Mr de Araujo.
Filomeno Aleixo, from Fretilin, said Father Martinho Gusmao had "clearly prejudiced the outcome of Monday's ballot".
Incumbent leader Xanana Gusmao has long indicated that he would not stand for re-election.
Earlier this week, the UN Security Council called on all parties to avoid violence amid clashes in and around the capital, Dili.
In May 2006, at least 33 people died and 150,000 fled their homes in street clashes around the capital Dili, after former Prime Minister Mari Alkatiri split the armed forces.