MOSCOW -- Escalating a confrontation with Russia, Turkey's prime minister said Thursday that Russian military equipment and munitions bound for Syria's Defense Ministry had been confiscated from a Syrian civilian jetliner on a Moscow-to-Damascus flight, which was forced to land in Ankara on suspicion of illicitly carrying war material.
The accusation by the prime minister, Recep Tayyip Erdogan, also inflamed Turkey's already difficult relationship with Syria, where a 19-month-old uprising against President Bashar al-Assad has expanded into a civil war that is threatening the stability of the Middle East.
Mr. Erdogan's accusation, reported by Turkey's semiofficial Anatolian News Agency, came only hours after the Russian Foreign Ministry accused the Turks of illegally searching the plane and demanded an explanation. A leading Russian arms export company denied that military equipment from Russia could have been aboard.
The Turks, saying they had acted on an intelligence tip, forced the Air Syria flight with 35 passengers aboard to land at an airport in the Turkish capital, Ankara, on Wednesday.
"From Russia, an institution equivalent to our Machinery and Chemical Industry has sent military tools, equipment and ammunition to the Syrian Defense Ministry," Mr. Erdogan was quoted as saying about the plane inspection. He was drawing a comparison to Turkey's Machinery and Chemical Industry Institution, or MKEK, a leading provider of defense equipment to the Turkish military.
"Upon the intelligence received, research there was conducted and it was unfortunately seen that there was such equipment inside," Mr. Erdogan said.
He did not further specify what precisely had been found.
Mr. Erdogan also said that an upcoming visit to Turkey by Russia's president, Vladimir V. Putin, had been postponed. He said the postponement had no connection with the forced grounding of the plane.
Earlier, Syria reacted for the first time to the disrupted flight of the Syria Air jetliner, which it said had been prevented from resuming its journey for eight hours. Syrian officials quoted by SANA, the official news agency, called the Turkish action illegal, accused the Turks of mistreating the crew and frightening the passengers, and said Syria would protest the incident to international aviation authorities.
Turkey's Foreign Ministry said Wednesday that the plane had been detained on suspicion of harboring weapons and said a number of unspecified cargo items "that infringed on international regulations" had been confiscated. But Mr. Erdogan's statement was the most detailed yet about what the Turks claimed to have found.
He spoke after Moscow had expressed dismay at the Turkish actions. A statement from Aleksandr K. Lukashevich, a Foreign Ministry spokesman, said the forced landing had "threatened the life and safety" of Russian citizens aboard and that Russia "continues to insist on an explanation of the reasons for these actions by the Turkish authorities."
Vyacheslav Davidenko, a spokesman for Rosoboronexport, the Russian company that has a monopoly on legal exports of finished weapons, denied any connection with what the Turks claimed to have found. "We don't know what cargo was on that plane, but the cargo, whatever it was, does not belong to Rosoboronexport," he said in a telephone interview.
Moscow's complaints were quickly rejected by Turkey's Foreign Ministry, which summoned the Russian ambassador and said the Turks had acted properly and had treated the passengers responsibly, the Anatolian News Agency reported.
Russia and Turkey are already at odds over the Syrian crisis, with Ankara joining Western and many Arab nations in support of insurgents seeking to overthrow Mr. Assad, while Moscow has consistently shielded Mr. Assad, its main regional ally.
Despite their differences -- and a cold-war history of animosity -- Russia has been striving in recent months to build its relationship with Turkey, which is one of Russia's largest trading partners and a key player in regional politics.
Mr. Erdogan visited Moscow in late July, and Mr. Putin's now-postponed reciprocal visit had been scheduled to take place in coming days.
Some Russian analysts said that they expected the two sides to step back from further confrontation over the forced landing.
Fyodor Lukyanov, editor in chief of the journal Russia in Global Affairs, said that though the two countries have assumed opposing positions in the Syrian crisis, Russian policy makers have accepted Turkey's stance because they view it as driven by domestic considerations. Tens of thousands of refugees have crossed the Turkish border as violence in Syria mounted, fueling grievances among Turks about their government's handling of the crisis.
"Now Turkey cannot be an outside observer and an outside force -- it's about Turkish stability," Mr. Lukyanov said. The relationship could suffer, he said, "if the crisis will escalate and Turkey will be more and more in the middle of the Syrian struggle. But so far, they will find a face-saving way to preserve the relationship."
Ellen Barry reported from Moscow, Anne Barnard from Beirut, Lebanon, and Sebnem Arsu from Hatay, Turkey. Reporting was contributed by Alan Cowell from Paris, Christine Hauser and Rick Gladstone from New York, and Hwaida Saad from Beirut.
Correction: October 11, 2012, Thursday
This article has been revised to reflect the following correction: Due to an editing error, an earlier version of this article referred incorrectly to Vladimir V. Putin, the Russian leader. He is president, not prime minister.
Correction: October 11, 2012, Thursday
This article has been revised to reflect the following correction: An earlier version of this article misattributed a quotation regarding allegations that a Syrian Air flight forced to land by Turkey was carrying Russian military equipment bound for Syria. It was Fyodor Lukyanov, a Russian foreign policy analyst – not Aleksandr K. Lukashevich, a spokesman for Russia's Foreign Ministry -- who said in an interview with Kommersant FM, a radio station: "Who could know that? According to Turkey, there was. The Russian side isn't saying anything exact, but I cannot rule out that something could have been there."
It was also Mr. Lukyanov, not Mr. Lukshevich, who said "I think that tension will now develop in the relationship between Russia and Turkey."
This article originally appeared in The New York Times.