Russia's Federal Security Service (FSB) confirmed on Monday that the twin crashes of airliners last week were caused by explosions, Interfax news agency reported.

    Andrei Fetisov, chief of the scientific and technical support department at the FSB said the explosions aboard the crashed passenger jets are now a fact confirmed by expert studies.

    Further study of the debris of both planes show that there had been explosions aboard the jets and that the explosive devices hadcontained hexogen.

    Two Russian passenger jets, Tu-134 and Tu-154, crashed almost simultaneously Tuesday night after taking off from Moscow's Domodedovo Airport, killing all the 90 people on board and raisingfears of terrorist attacks.

    Investigators also said that two Chechen women bought tickets at the last minute for the flights at the airport Tuesday and thattheir bodies were the only ones unclaimed by relatives so far -- raising suspicion that they may have been suicide bombers.

    A group called Islambouli Brigades has claimed responsibility for the air crashes, linking the disasters to the situations in Russia's breakaway republic of Chechnya.