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Two Russian Tupolev airliners crashed almost simultaneously on Tuesday, killing all 89 people on board. The planes had both left Moscow's Domodedovo airport.

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They both disappeared from radar screens at about 1900 GMT, coming down in southern Russia.

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Relatives faced an anxious wait for news of those on board the two flights.

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Russia held a day of mourning on Thursday for the 89 crash victims as investigators searched the debris.

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One plane sent out a distress signal shortly before vanishing. The Sibir airline said it had been a hijack alert.

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Experts are struggling to gather data from the planes' black box flight recorders.

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The FSB security service says traces of explosives were found at one of the crash sites.

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Security has been stepped up at Russian airports, ahead of Chechen presidential elections on Sunday.