A man who was killed before he could testify at the International Criminal Court's trial of Kenya's deputy president was involved in attempts to tamper with prosecution witnesses, the court's prosecutors alleged on Friday.

Prosecutors said Meshack Yebei, who was found dead in Kenya last week, had been considered as a prosecution witness at the trial of Kenyan Deputy President William Ruto.

However he was dropped after prosecutors discovered he was "deeply involved in the scheme to corrupt prosecution witnesses," the statement said.

Ruto is facing charges at the court in The Hague of fomenting ethnic violence after Kenya's 2007 election.

Prosecutors dropped similar charges against President Uhuru Kenyatta last month after acknowledging witness withdrawals had left them without the evidence they needed to make the case.

Prosecutors said many of their witnesses against the two men had been threatened or bribed into withdrawing incriminatory testimony.

Kenyan authorities are currently investigating the killing of Yebei, who after his dismissal by prosecutors was summoned by Ruto's lawyers as a "crucial" defence witness.

"Any suggestion that the Office of the Prosecutor was involved in Mr. Yebei's alleged abduction and murder is both outrageous and utterly false," prosecutors said.

Reuters