Sergei Yastrzhembsky, aide to Russia's President Vladimir Putin, addressed a roundtable in Brussels to comment on the controversy.
Russia previously disproved the suspicions, he said to a Novosti reporter.
As soon as Yandarbiev found refuge in Qatar, Russia demanded him extradited as international terrorist. The host country's authorities flatly refused to do that.
Notable for links with the Al-Qaeda and other Muslim extremist organizations, Zelimkhan Yandarbiev was on an United Nations black list of international terrorists together with Shamil Basayev, the most notorious of Chechen terrorists. Yandarbiev was on the Russian and international "wanted" lists, stressed Mr. Yastrzhembsky.
The three Russians - all in Qatar on business missions - were detained on the Russian ambassadorial premises in Doha in the small hours February 19. One of them was eventually released, and is now staying at the embassy.
The suspects are certainly innocent, says Igor Ivanov, Russia's acting Minister of Foreign Affairs. Neither the unlucky three nor their entire country had a slightest involvement in the Yandarbiev assassination, he firmly said to newsmen.
When asked just what secret agencies the detainees were working for, Mr. Ivanov replied:
"All Russian secret services, just as their analogues throughout the world, are fighting international terrorism. All are collecting and processing information to enhance efficiency of the cause. That work has every justification and strictly complies with host countries' laws."