All passengers aboard the Russian Tu-154 airliner which went missing and later crashed on Tuesday night were killed, Itar-Tass news agency cited Russian official sources as reporting.

   According to preliminary investigation, the wreckage of the jet has been discovered in southern Russia's Rostov region, the Emergency Situations Ministry said Wednesday.

   Forty-four people including the crew on board were killed, the local government said.

   The bodies of approximately 20 people were found at the crash scene, said Natalya Vlasenko, press secretary for the Rostov region's emergency situations office.

   Earlier reports said the plane carried 38 passengers and eight crew members.

   Interfax reported that the Tu-154 sent a distress signal indicating an attack or hijacking just before it disappeared in southern Russia, but it later quoted an unnamed law enforcement source as saying that the signal was an SOS and no other signals were sent.

   Almost at the same time, a passenger jet Tu-134 crashed in the Tula region south of Moscow, killing all the 35 passengers and eight crew on board.

   The Tupolev aircraft was en route from Moscow to Russia's southern city of Volgograd when it disappeared from radar screens at about 23:00 Moscow time (1900 GMT) Tuesday.  

   The ministry said flight recorders of both planes have been found.

   Nearly 90 passengers and crew members were reported to be aboard both airliners and there have been no reports of survivors from either plane so far.

   There were no Chinese citizens aboard the two planes, the Chinese embassy in Russia confirmed Wednesday.

   Prosecutors have opened criminal cases on the crashes of the two jets and terrorist attacks are being considered as possible causes of the air disasters. 

   Security has been tightened at all of Russia's airports and the Interior Ministry has promised to take additional measures to maintain safety at public places, especially airports and railway stations.