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 Kremlin accused the Turks of illegally grounding and searching the plane. 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.

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