Russia furiously demanded answers from Turkey on Thursday after it forced a Syrian passenger plane flying from Moscow to land in Ankara on suspicion of carrying "illegal cargo", reportedly weapons, to Damascus.
Turkey's action on Wednesday risks not only inflaming tensions with Syria but also hurting ties between Ankara and Moscow which have starkly differing views on the Syria conflict.
And President Vladmir Putin's spokesman said Thursday the Russian leader has postponed a planned visit to Turkey, without giving the reason for the delay.
The trip had been reportedly scheduled for October 15 although the first media reports of the postponement surfaced before plane was intercepted on Wednesday.
Turkey scrambled two jets to force down the Syrian Air Airbus A-320 after reportedly receiving intelligence it was carrying military cargo for the regime of Syrian President Bashar al-Assad.
Russia, a top ally of the Damascus regime and its biggest arms supplier, said Ankara had put the lives of passengers -- who included Russian citizens -- at risk by forcing it to land in the Turkish capital, and denied it was carrying arms or military equipment.
"We are concerned that this emergency situation put at risk the lives and safety of passengers, who included 17 Russian citizens," said a statement by foreign ministry spokesman Alexander Lukashevich.
"The Russian side continues to insist on an explanation of the reasons for such actions by the Turkish authorities toward Russian citizens and to take measures to exclude such incidents in the future," he added.
Turkish Foreign Minister Ahmet Davutoglu said Turkey had seized "illegal cargo" from the plane, adding that Turkey would hold on to it for further investigation but declining to elaborate on the contents, the Anatolia news agency reported.
The confiscated cargo was believed to be missile parts, the Turkish NTV news channel reported, while state-run TRT speculated it could be communications equipment headed for Damascus.
A source in the Russian arms export industry denied the claims.
"Neither weapons nor any systems or assembly parts for military equipment were or could have been on board the passenger plane," the unidentified high-ranking source fold Interfax.
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Russia has infuriated Turkey and its Western allies by refusing to halt military cooperation with Syria, one of its key weapons clients, despite the raging conflict in the country.
Ties between the one-time allies Syria and Turkey have soured dramatically over the conflict, particularly when a Turkish fighter jet was brought down by Syrian fire in June, killing two pilots.
Turkey has also sent in major troop and arms reinforcements to the border with Syria and warned of strong retaliation after a series of shell strikes on its soil, including a deadly attack last week that left two women and three children dead.
The sabre-rattling added to growing fears of a wider regional fallout from the conflict ravaging Syria, in which activists say more than 32,000 people have died since March 2011.
Earlier this month, Iraq stopped and searched a Syria-bound Iranian cargo plane but allowed it to continue as no prohibited items were found.
And in June, Britain forced a Russian cargo vessel allegedly carrying attack helicopters and missiles for Syria to turn back.
Turkey and Russia have starkly different views on the Syria conflict, with Moscow defiantly refusing to take sides against Assad's regime which Turkish Prime Minister Recep Tayyip Erdogan has vehemently condemned.
But Davutoglu said "the incident would not affect Turkish-Russian relations at this point".
However, in a sign of the tensions the plane intercept could cause, the Russian foreign ministry also listed a number of what it saw as serious shortcomings by the Turkish authorities in their handling of the incident.
"The Turkish side did not inform the Russian embassy in Ankara that there are Russian citizens among the detained plane's passengers," it said. "We found out about this from news websites."
It said the Turkish authorities denied Russian diplomats a meeting with the Russian citizens, without an explanation.
The Russian passengers had to spend eight hours on the plane without food and were not permitted to go inside the airport, only to rarely exit the plane and go down to the landing strip, the statement said.
According to Anatolia, the plane was allowed to leave at 2330 GMT, nine hours after it was intercepted, with all of its 35 passengers on board.