Two Russian passenger planes crashed almost simultaneously late on Tuesday night killing all?89 on board, and security officials said they were investigating a possible terrorist attack.

The planes disappeared from air traffic controllers' radar screens within minutes of each other and one Tu-154, carrying 46 passengers and crew, sent a hijack alarm before crashing near the southern Russian city of Rostov-on-Don.

President Vladimir Putin ordered the FSB security service to investigate the crashes, which came before Sunday's presidential election in Chechnya where separatists have threatened to disrupt the poll with violence. Yesterday Putin returned to Moscow from the Black Sea resort of Sochi hours after the crash.

"The fact that both planes took off from one airport and disappeared from radars around the same time can show it was a planned action," the Interfax news agency quoted an aviation source as saying. "In such a situation one could not exclude a terrorist act."

Witnesses on the ground heard an explosion on board the second plane, a Tu-134 carrying?43 passengers and crew, just before it crashed near Tula, 150 kilometers south of Moscow.

There were no foreigners on board the planes, which both took off from Moscow's Domodedovo airport.

"Around 11 pm, give or take five minutes, there was this strange noise in the sky, then this torn-up book fell onto our garage," a local man told NTV television, holding up the book with its tattered pages.

The Interfax news agency said emergency workers spotted a fire about 965 kilometres south of Moscow in the region where the second plane went missing.

News agencies quoted security officials saying they could not rule out terrorism, while Rostov prosecutors opened a criminal probe into the crash of the Sibir Airlines Tu-154 en route to the Black Sea resort of Sochi.

"A minute before the plane disappeared from the radar screens the interior ministry received a report from an air traffic controller that there had been an attack on the crew," Interfax quoted an Interior Ministry official as saying.

A spokesman said: "We are considering an act of terror as one possibility, especially after we received an automatically generated message from the Sochi air control centre that the plane had been hijacked."

The incidents came against a backdrop of mounting violence in Chechnya, where Moscow has been battling separatists for a decade. Rebels launched a major raid in the local capital Grozny last week and have promised more attacks.

The plane which crashed near Tula, operated by Volga-Aviaexpress, came down after nearly reaching its cruising altitude. The company said the plane was in good shape and its passengers had undergone all necessary security checks.

"I rule out pilot error, because even in the most serious conditions which can affect this kind of plane, such as loss of control or fire, the crew always has time to pass on information to the ground," Yuri Dmitriev, director of Volgograd airport, told Russia's Channel One television.

An Emergencies Ministry spokeswoman said there was no chance of anyone surviving as the plane fell from 10,000 metres. Wreckage was spread over several kilometres with some pieces about the size of a car, TV footage showed.

Three minutes after the Volga-Aviaexpress Tu-134 crashed, air traffic controllers lost contact with the Sibir Tu-154. Its wreckage was not found until yesterday morning.

Emergencies Minister Sergei Shoigu told Russian television that nearly all of the victims' bodies had been found, and flight recorders from both planes had been recovered.

Details of crashed planes

Below is key information about the two flights:

Moscow-Sochi:

Airline: Sibir Airlines

Flight number: 1047

Aircraft type: Tu-154

Passengers: 46 people including eight crew

Left Moscow's Domodedovo airport at 9:35 pm (1735 GMT)

Contact lost at 10:59 pm (1859 GMT)

Estimated crash location: about 140 kilometres from the city of Rostov-on-Don, near the Ukrainian border.

Moscow-Volgograd:

Airline: Volga-Aviaexpress

Flight number: 1303

Aircraft type: Tu-134

Passengers:?43 including?eight crew

Left Moscow's Domodedovo airport at 10:15 pm (1815 GMT)

Contact lost at 10:56 pm (1856 GMT)

Estimated crash location: Tula region, near the village of Buchalka.

(China Daily August 26, 2004)