Thousands were left homeless after weeks of ethnic violence
Kenyans testifying about violence that swept the country after the 2007 election have been subjected to death threats and attacks in recent days.
One witness told the BBC how he had received death threats by text message since giving evidence to a high-level commission investigating the violence.
Other reports say witnesses have been beaten and told to withdraw testimony.
The clashes between December 2007 and February 2008 left 1,300 people dead and forced 300,000 from their homes.
The International Criminal Court (ICC) has promised to prosecute the main perpetrators.
The ICC is yet to name any suspects though, and witnesses have so far given evidence only to the Waki Commission, set up by the Kenyan government.
But in recent weeks there have been several reports of intimidation.
One witness told the BBC's Network Africa programme he received threats verbally and by text message after he spoke to the Waki Commission.
"The first message said: 'You are still a young man and you are not supposed to die, but you betrayed our leader, so what we shall do to you is just to kill you,'" he said.
The witness said he had been forced to leave his home and go into hiding, but promised to testify despite believing both he and his family were in danger.
The Nairobi Star newspaper reported that several other witnesses had been viciously attacked.
The paper referred to one man, known as Witness A, who told them he was hauled out of a taxi on 28 December and beaten senseless by four men.
"They told me that unless I withdraw my evidence from Waki they will return to kill me," Witness A told the paper.
He said he had now fled the country after his cousin was murdered by the gang.
The international community had urged Kenya to move swiftly in punishing perpetrators of the post-election violence, but no-one has yet been charged.
In November, the ICC's chief prosecutor Luis Moreno Ocampo announced he would take on the cases of the main suspects.
He said two or three cases could come to trial in The Hague by July.
Prominent Kenyan politicians, including cabinet ministers, are believed to be among the suspects.
President Mwai Kibaki and Prime Minister Raila Odinga agreed to share power to end the clashes that followed the 2007 election.
Mr Kibaki won the election, but Mr Odinga's supporters alleged fraud.
Clashes between their supporters snowballed into large-scale ethnic violence that engulfed large parts of the country for weeks.