Russia kept up an angry flow of rhetoric Friday directed at Turkey, demanding that Turkish authorities reveal exactly what type of Russian "munitions" they claim to have found aboard a Syrian airliner forced down over Turkey on Wednesday.

The Russian Foreign Ministry also complained in a statement that the takedown of the jet was illegal, and that it "endangered the lives and safety" of 17 Russian passengers, who the ministry claims were subsequently mistreated and denied access to Russian consular officials for over 8 hours.

The incident comes amid growing confusion in Russia-Turkish relations. On Monday, two days before the aircraft was forced down, Russian President Vladimir Putin cancelled a state visit to Turkey that was to have begun early next week. Turkish officials would only say the trip was shelved due to "red tape."

"Relations between Russia and Turkey have been improving for the past several years, after decades of being on opposite sides of the cold war barricades," says Pavel Shlykov, an expert with the official Institute of Asia and Africa in Moscow.

"I really hope this incident with the plane doesn't affect the positive trend," he adds.

But the mystery surrounding the cargo that was aboard the Syrian A-320 airbus that was compelled to land by Turkish jet fighters may have been cleared up, with an admission by Russian arms officials that materials for use in Syrian anti-aircraft radars may have been aboard.

On Friday, the Moscow business daily Kommersant, citing unnamed Russian arms industry officials, said the plane was carrying 12 boxes of electronic components for use in Syrian air defense systems, along with legal documentation for the equipment.

The most alarming issue for the Kremlin appears to be the effectiveness of Western intelligence sources, whom they blame for alerting Turkish authorities about the presence of the electronic parts aboard the Airbus.

"The Turkish authorities sent out two F-16 fighters to escort the jet so they most likely knew about the cargo that was being carried," an official of the Russian FSB security service told Kommersant. "They would not have done this if they had not been sure."

Moscow was previously blindsided back in July when British authorities stopped a ship carrying Russian attack helicopters to Syria by forcing its insurance company to pull coverage. The helicopters were sold to Syria in the 1990s but were being serviced in Russia and quietly sent back aboard a civilian vessel.

"With that story about the helicopters, and now this, we have to assume that US intelligence has very good channels of information in Russia," says Alexander Golts, military columnist for the online newspaper Yezhednevny Zhurnal.

"This has got to be the cause of considerable worry," in the Russian secret services, he adds.

Kommersant's sources insisted that the components aboard the Syrian jetliner were not arms, and that it was perfectly legal to carry radio equipment on a civil airliner if it was shut off. "It is not weaponry. What is the problem about carrying a switched-off radio receiver on board an airliner, if it does not represent any threat to the plane or passengers?" one official told the newspaper.

"We did not violate any international laws," said another.

The newspaper also quoted Vyacheslav Davidenko, the spokesman of Russia's official arms export agency Rosoboronexport, as saying that "there was no cargo belonging to us" aboard the plane.

On Thursday, Turkish Prime Minister Recep Tayyip Erdogan justified the plane's takedown saying "one cannot carry defense industry equipment or arms, munitions (aboard) civilian aircraft.... Unfortunately this rule was violated."

Vladimir Sazhin, an expert with the official Institute of Oriental Studies in Moscow says the legalities of the situation are murky on both sides.

"Russia's position is that it's illegal to force a plane to land in this way. It's only done if an aircraft diverges from its assigned route or it represents a threat to the country it's flying over," he says.

"On the other hand, it does seem that if the plane was carrying radar parts from air defense systems, as reported, then that's a military cargo that shouldn't be hauled aboard a civilian plane. Now it's up to lawyers to sort it out," he adds.

Mr. Golts says that selling arms to Syria is not illegal – as Russian officials have repeatedly underscored – because no such sanctions have been passed by the UN Security Council.

Many Russian experts argue that it's difficult to take Turkish indignation seriously, since Turkey allows its territory to be used as a staging area and supply conduit by Syrian rebels.

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Golts adds that the Kremlin's stubborn and consistent backing for Syrian strongman Bashar al-Assad is out of step with much of the world community.

"Russia's ongoing support for Assad is totally ideological," says Golts. "Putin is certain that all this turmoil with the Arab Spring is the result of a CIA conspiracy, and he sees it as his personal duty to struggle against it."