Russian security agency FSB said Wednesday that it arrested a group of immigrants from Central Asian countries on suspicion of planning a series of terror attacks during the May 9 Victory Day celebrations. The agency said the attacks were ordered by the leaders of international terrorist organizations based in Syria and Turkey, Agence France-Presse (AFP) reported, citing the FSB.

“We have found a large quantity of weapons, explosives and other terrorist equipment,” the FSB, said in a Russian-language statement, according to “The suspects were planning to fire weapons into a crowd, during mass street celebrations on May 9,” a source at FSB reportedly told Russia's RIA Novosti news agency.

The arrested suspects have been taken to the central FSB office at Lubyanka in Moscow, reported, adding that those arrested “are progressing towards making confessions.”

On Sunday, Russia marked Labor Day that saw several high-profile cultural and political events near Moscow. Moreover, the Russian Orthodox Church celebrated Easter on the same day.

According to AFP, hundreds of thousands of people usually arrive at Moscow for a military parade and other celebrations to mark the anniversary of victory over Nazi Germany in the World War II.

Russia has supported Syrian President Bashar Assad in his offensive against rebels, and helped the Middle Eastern country to recapture the ancient city of Palmyra from the Islamic State group in March. The U.S. and allies have accused Russia of carrying out air campaign against the Syrian rebels in garb of strikes against ISIS militants. However, Russia has consistently denied the accusation.