Foreign fighters detained on Sunday in Russia's southern region of Dagestan were involved in financing a deadly attack on a concert hall near Moscow last month, the TASS news agency cited Russia's FSB state security service as saying on Monday.
The FSB also said that one of the four detained men had confessed to personally bringing weapons to the Moscow attackers, according to the Interfax news agency.
Russian authorities said on Sunday they had detained a group of men who were planning violent acts, but had provided no information on their nationality.
At least 144 people were killed in the March 22 attack. IS has claimed responsibility but Russia has also said it believes "Ukrainian nationalists" were linked to the attack, an assertion strongly denied by Kyiv.
The four men Russia has charged with carrying out the attack are ethnic Tajiks.
Search expands after Philippine ferry fire kills five and leaves dozens missing
US military says it struck vessel in Caribbean, killing 3
At least 14 killed in explosion at weapons depot in Syria
US hits five Iranian oil tankers after attack on Navy ships
UK gives air traffic provider a week to probe outage that halted flights
Serbia's President Vucic dissolves parliament, calls snap elections
With large crowds attending, Norway lays King Harald to rest
Jordan intercepts 18 Iranian ballistic missiles
