MOSCOW — Escalating a confrontation with Russia, Turkey’s prime minister said Thursday that Russian military equipment and ammunition 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 further inflamed Turkey’s already difficult relationship with Syria, where a 19-month-old uprising against President Bashar Assad has expanded into a civil war that is threatening the stability of the Middle East.
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 Ankara airport Wednesday.
“From Russia, an institution equivalent to our Machinery and Chemistry Industry has sent military tools, equipment, and ammunition to the Syrian Defense Ministry,’’ Erdogan was quoted as saying about the plane inspection. He was drawing a comparison to Turkey’s Machinery and Chemical Industry Institution, 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,’’ Erdogan said.
He did not further specify what had been found.
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 Erdogan’s statement was the most detailed yet about what the Turks claimed to have found.
He spoke after Moscow expressed dismay at the Turkish actions. A statement from Alexander 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 said they 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 Assad, while Moscow has consistently shielded 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.
Erdogan visited Moscow in late July, and Putin’s now-postponed reciprocal visit had been scheduled to take place in the coming days.
Some Russian analysts said they expect 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 policymakers 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.