Terrorism, human error or mechanical mishap could have caused one of Russia's worst air tragedies in which two planes crashed almost simultaneously and killed at least 89 people, officials said on Wednesday.
President Vladimir Putin, acting swiftly before Sunday's presidential poll in rebel Chechnya, ordered the tightening of security at all Moscow's airports and put the Interior Ministry in charge of screening procedures.
Prosecutor General Vladimir Ustinov told Putin he had no clear view of what happened to the planes, which took off from Moscow's Domodedovo Airport late on Tuesday around an hour apart for two different destinations.
They crashed within four minutes of each other.
"We are examining a number of versions, among them a terrorist act, and human and technical factors," Ustinov told Putin during a meeting with the heads of the FSB security service and the Emergencies Ministry shown on television.
A Tu-134 flying to Volgograd went down near the town of Tula south of Moscow. Within minutes and 800 km (500 miles) away, a Tu-154 bound for the Black Sea resort of Sochi crashed near the southern town of Rostov-on-Don.
The owner of the Tu-154, Sibir Airlines, said the pilots had triggered a hijack alert just before their plane crashed and the aircraft seemed to have exploded in mid-air. It was carrying 46 passengers and crew.
Volga-Aviaexpress, a small regional carrier which owned the Tu-134, said the crew did not report any problems on board before the plane crashed with 43 passengers and crew. The Emergencies Ministry later said 44 people were aboard.
Aided with cranes, investigators sieved through high grasses in almost identical countryside near the two sites. Huge slabs of twisted metal, seats and the odd piece of clothing were scattered over dozens of miles.
FSB IN CHARGE
Putin, who broke off his summer break in the Black Sea resort of Sochi to return to Moscow, had ordered the FSB to investigate the case, which it is normally only asked to do if terrorism is suspected.
He also ordered the government to transfer airport security measures to officers from the Interior Ministry and declared Thursday a national day of mourning.
Fear of attacks in Russia is high ahead of Chechnya's election. Separatist rebels have vowed to disrupt the poll.
Analysts said the chance of two planes crashing within minutes must have been more than a coincidental malfunction. "It's freaky if it is not sabotage," said David Learmount, operations/safety editor at Flight International magazine.
The crashes came against a backdrop of violence in Chechnya, where Moscow has been battling separatists for a decade. Rebels launched a major raid in the local capital Grozny last week.
Moderate Chechen separatists denied any role in the crashes.
Asked if his group was responsible for the crashes, Akhmed Zakayev, a spokesman for Chechnya's separatist leader Aslan Maskhadov, said: "Of course not. To us any form of terrorism is absolutely unacceptable. We have condemned it and continue to condemn it".
One Middle East intelligence expert, who had no direct knowledge of the crashes, said the "first indications are that this is an operation by al Qaeda or a local sympathiser group". He said al Qaeda had been trying to make inroads in Chechnya.
Witnesses on the ground heard an explosion from the Tu-134 before it crashed 150 km (90 miles) south of Moscow.
"Around 11 p.m. (1900 GMT), 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.
Local prosecutors opened criminal probes into both crashes. Investigators recovered the flight recorders from both planes and sent them to Moscow for analysis. Television reported officials hoped to have retrieved the information by Thursday.
