key "insider" witness who testified against Charles Taylor has gone into hiding after being threatened for giving evidence at the former Liberian president's war crimes trial, the chief prosecutor said Thursday.

Varmuyan Sherif, a former bodyguard for Taylor, and his family have been relocated since he testified in January in The Hague, said Stephen Rapp of the Special Court for Sierra Leone.

The threats, which are being investigated by police and United Nations officials in Liberia, underscore fears voiced by prosecutors before the

 trial that witnesses could be endangered by testifying against Taylor, who still has a wide network of supporters in Liberia.

Rapp said rocks were thrown at Sherif's home in Liberia and a threatening letter was sent to his brother after Sherif testified that Taylor smuggled arms, cash and communications equipment to one of the most notoriously brutal militias in the Sierra Leone war.

"He has been temporarily relocated and efforts are ongoing to determine whether it's safe for him to return or whether he needs to be permanently relocated," Rapp said in an interview with The Associated Press.

Sherif is not the only witness targeted, he said.

"We have had other instances of witnesses being threatened and written communications being delivered to their homes," Rapp said.

That has made some witnesses wary of appearing in the Hague courtroom where Taylor is being tried by the U.N.-backed court.

"There are situations where if witnesses can't testify in closed session it's going to be very, very difficult to persuade them to testify," Rapp said.

Several witnesses at the Taylor trial already have testified behind closed doors because of fears of reprisals.

Rapp, who has been in Africa for most of the trial, said he was pleased with the case so far.

He said the Taylor prosecution was given a significant boost last week by a ruling from the court's appeals chamber that said rebels linked to Taylor were part of an organized plot, known as a joint criminal enterprise, to seize control of Sierra Leone with a campaign of terror and loot its diamond mines.

Trial judges in Sierra Leone last year ruled that prosecutors did not correctly set out the joint criminal enterprise allegations in an indictment against three rebels who were tried separately from Taylor, but appeals judges overturned that ruling last Friday.

"It's enormously significant to us in this case," Rapp said. "The biggest victory we've had to date in the Taylor trial was the decision by the appeal chamber in Freetown last Friday."

Taylor has pleaded not guilty to charges that include murder, rape, torture, enlisting child soldiers and pillaging towns and villages during Sierra Leone's 10-year civil war that ended in 2002.

His trial is being held in a courtroom rented from the International Criminal Court in the Hague because of fears prosecuting him in Sierra Leone could spark new violence.

Rapp was visiting The Hague on his way to England, where he will discuss with officials efforts to track down millions of dollars Taylor is believed to have syphoned into foreign bank accounts while he ruled Liberia from 1997-2003.

"We have got information that millions of dollars passed through his personal accounts -maybe even more money than Liberian's government was receiving at the time he was president -and evidence of wire transfers being made around the world," Rapp said.

Taylor claims to be broke and the court, funded by voluntary contributions from countries around the world, is footing the bill -expected to run to $2 million for his defense team.

If investigators can trace and seize embezzled cash, it could be used not only to pay his legal bills, but also to aid thousands of victims mutilated by rebels in Sierra Leone notorious for hacking off their enemies' limbs.

"That money could come back and be put into programs to help amputees," Rapp said.