Western countries accused Moscow on Monday of preventing inspectors from reaching the site of a suspected poison gas attack in Syria and said Russians or Syrians may have tampered with evidence on the ground.
"It is our understanding the Russians may have visited the attack site," US Ambassador Kenneth Ward said at a meeting of the OPCW in The Hague on Monday.
"It is our concern that they may have tampered with it with the intent of thwarting the efforts of the OPCW Fact-Finding Mission to conduct an effective investigation," he said. His comments at the closed-door meeting were obtained by Reuters.
Russian Foreign Minister Sergei Lavrov denied that Moscow had interfered with any evidence: "I can guarantee that Russia has not tampered with the site," he told the BBC in an interview.