Russian President Vladimir Putin has ordered the country's top security agency to investigate nearly simultaneous crashes of two passenger planes, which flew out of Moscow late Tuesday.
Emergency officials in Russia found the wreckage of the second of two airliners which crashed after taking off from the same Moscow airport, late Tuesday. The causes of the crashes are still unknown. Officials say all passengers and crew aboard the two planes - some 90 people - were killed.
Rescue teams have located the wreckage of a Tupolev-154 plane which went missing in the Rostov-on-Don region of southern Russia, with 46 people on board.
The plane was on a flight from Moscow to the Black Sea resort city, Sochi, when it disappeared from radar screens around the same time that a second aircraft was also reported missing.
The wreckage of that plane, a smaller Tupolev-134, was found in the Tula region, some 180 kilometers south of Moscow, while on its way to the city of Volgograd.
Russian news agencies report investigators so far have found no evidence of terrorism in the wreckage, but they have not ruled it out as a cause. Investigators have recovered the flight recorders from the crash sites of both planes.
Both planes had left the same airport in southern Moscow, then dropped off of radar screens within minutes of each other. One plane had reportedly activated a generic distress signal before crashing.
People living near the site of the Tula crash report hearing an explosion shortly before the Tu-134 went down.
Soon after hearing that two planes had gone missing, President Vladimir Putin ordered security tightened at all airports, across the country.
Terrorist bombings have occurred in recent years in Moscow and other cities in southern Russia, near the breakaway region, Chechnya, where Russian troops have been battling separatist rebels for most of the past decade.
A presidential election is to be held in Chechnya, Sunday, to replace the former Chechen president who was assassinated in a bomb attack last May, and authorities have warned that violence may increase in the run-up to the vote.
However, mechanical problems have not been ruled out in the two crashes.
Many aircraft in Russia's aging fleet are old, especially planes such as the two Tupolev's, which are designed for short-range flights.