The International Criminal Court has issued an arrest warrant for a Kenyan man suspected of tampering with witnesses in the war crimes case against Kenya's Deputy President William Ruto.

Judge Cuno Tarfusser at the Netherlands-based court in the Hague said on Wednesday that 41-year-old journalist Walter Barasa is suspected of attempting to bribe a potential witness. It is the first time the court has sought to prosecute someone for interfering with the legal process.

"The evidence collected so far indicates that there is a network of people who are trying to sabotage the case against Mr Ruto ... by interfering with prosecution witnesses," the case's prosecutor Fatou Bensouda said in a statement.

Barasa allegedly offered to pay three witnesses at least $16,000 to withdraw as ICC prosecution witnesses.

He is described in court documents as a "former intermediary for the prosecution" in Kenya, meaning he liaised between witnesses and ICC prosecutors.

"I deny any such charges," Barasa told Reuters news agency. "I have not gotten in touch with any witnesses or anybody having any intention of asking them or bribing them to pull out of the case."

Ruto, whose trial began last month, and President Uhuru Kenyatta are charged separately with orchestrating violence that swept Kenya after contested elections in 2007 and in which 1,200 people were killed. Kenyatta's trial starts in November.

Several witnesses have withdrawn, with prosecutors alleging intimidation and defence lawyers denying it. In March, the loss of a key witness led to the collapse of the case against Kenyatta's co-accused, the former civil service head, Francis Muthaura.

Source: Agencies