"We guarantee that the trials were taken by the experts who didn't leave hold on them before delivering them into a lab," Lavrov told reporters after talks with his Belarussian counterpart Vladimir Makei.

　　He noted that the experts' report consisted of over 80 pages of formulas and photographs with precise descriptions of the geographical location of the places the trials were taken.

　　"Our investigation was made in 100-percent accordance to the standards existed in the Organization for Prohibition of Chemical Weapons," the Interfax news agency quoted him as saying.

　　The minister urged relevant parties not to take advantage of Syrian opposition's use of chemical weapons to achieve some diplomatic and geopolitical goals.

　　"The only consequence of these developments for the prospective of the international conference (on Syria) is a necessity to spur the process of persuasion of the opposition to participate in the conference without preconditions," Lavrov said.

　　He added that the western countries had taken an obligation to persuade Syrian opposition to arrive in Geneva without preconditions.

　　On Tuesday, Russia said it had forensic proof that rebels had used a "lethal" sarin compound and handed its evidence to the UN team for inquiry.

　　Russia said sarin was in a projectile fired by the opposition into the Khan al-Asal section of Aleppo on March 19. Some 200 people were killed in the attack.