(AFP) - War crimes judges on Tuesday threw out charges of crimes against humanity against Kenya's Deputy President William Ruto over his alleged role in post-election bloodshed in 2007-2008, but left the door open to a possible new trial.

In a fresh blow to the prosecution, the judges at the International Criminal Court (ICC) ruled the charges against Ruto and his co-accused Joshua arap Sang "are vacated".

Ruto, 49, and Sang, 40, had both denied three counts of crimes against humanity -- namely murder, forcible deportation and persecution.

The two men were however "discharged without prejudice to their prosecution afresh in the future," the judges said, as the presiding judge slammed a "troubling" pattern of "witness interference".

Chief prosecutor Fatou Bensouda said her case had been "eroded by a perfect storm of witness interference and politicisation" adding the intimidation of witnesses had been "methodical, far-reaching and exceptionally well-resourced."

The decision was also met with dismay by rights groups and the victims of the violence unleashed by the disputed December 2007 elections, which left hundreds dead.

"There is no doubt that this will come as a disappointment for victims," Wilfred Nderitu, the lawyer representing the victims, told reporters in Nairobi, urging Bensouda to appeal.

Human Rights Watch senior legal adviser Elizabeth Evenson said: "The end of this case leaves victims bereft of justice and the help they need."

- 'Political meddling' -

The chamber concluded "the prosecution did not present sufficient evidence on which a reasonable trial chamber could convict the accused," the ICC said in a statement.

The majority decision to drop the charges by two out of the three judges came in a complex 253-page ruling.

Presiding judge Chile Eboe-Osuji said he had wanted to declare "a mistrial due to the troubling incidence of witness interference and intolerable political meddling".

But his colleague argued separately the two men should have been acquitted, while the third judge opposed the move to throw out the charges concluding the "prosecution case had not 'broken down' and ... there is sufficient evidence" to convict the two men.

Prosecutors, who allege more than 1,300 people died and some 600,000 others were left homeless in Kenya's worst wave of violence since independence from Britain in 1963, could still appeal Tuesday's ruling.

The case has been keenly watched in Kenya, which has led a high-profile campaign against the ICC among African nations, accusing the tribunal of bias against the continent.

President Uhuru Kenyatta, whose parallel ICC case was dropped in December 2014, welcomed the ruling saying he and Ruto had "endured a painful journey with the ICC" and had cooperated fully with the tribunal based in The Hague.

"This decision brings to a close what has been a nightmare for my nation," Kenyatta added in a statement.

- 'Free at last' -

On Ruto's home turf in Kenya's Rift Valley -- the site of some of the worst of the election violence -- there were celebrations as residents took to the streets of Eldoret in joy waving placards reading "Free At Last", "No Case To Answer" and "The Power of Prayer".

"This is a big day for us, Ruto is finally free," said Margaret Rotich.

But the victims had little to celebrate. "What the ICC should now tell us is who was behind the post-election violence," said Rogers Mwai, who was forced from his home by the fighting and now lives in an informal settlement outside Nakuru town.

"If it wasn't Ruto and it wasn't Uhuru (Kenyatta), then who was it?"

In an early victory for Ruto and Sang, judges barred the prosecution in February from applying amended ICC rules and using recanted testimonies in their case. The prosecution had said the recanted testimonies were key to their case.

Sixteen out of the 42 witnesses had changed their stories or refused point blank to testify, which the prosecutors alleged was due to intimidation, bribery or fear of reprisals.

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