Erdogan also said a Russian agency sent the material to Syria, and the flight violated international law, the Hurriyet Daily News reported.
Erdogan's statements came as Russia demanded explanations from Turkey after a Syrian plane traveling from Moscow to Damascus was grounded and its cargo seized, a Russian official said.
"Russian arms exporting agency was the sender and the receiver was the Syrian Defense Ministry. The material has been confiscated and is being examined," Erdogan told a news conference after talks with Kazakh President Nursultan Nazarbayev.
The airliner was forced down Wednesday.
The Turkish prime minister rejected suggestions Russian President Vladimir Putin's postponement of a visit to Turkey, scheduled for next week, was related to the airliner incident.
Erdogan said the two leaders jointly decided to postpone the visit when talking by telephone earlier this week, Hurriyet reported.
Alexander Lukashevich, a Russian Foreign Ministry spokesman, told the Interfax news agency Thursday his country "insists that the Turkish authorities must explain their conduct regarding the Russian citizens and prevent similar incidents in the future."
Lukashevich said Russian passengers aboard the plane were denied access to Russian consular officials and weren't supplied with food.
Syrian Transport Minister Mahmoud Said accused Turkey of air piracy. In an interview on the Hezbollah-affiliated al-Manar television station Thursday, he declared Turkey's actions violated civil aviation treaties.
Turkish authorities late Wednesday grounded a Syrian Air A-320 Airbus with 35 passengers on board for about eight hours on suspicion it was carrying military equipment destined for Syria, the Turkish daily Hurriyet Daily News said. Turkish fighter jets escorted the plane to an airport in Ankara, where authorities searched the plane's cargo.
Some passengers claimed they were beaten by Turkish officials and forced to sign papers indicating the plane made an emergency landing, the newspaper said.
Turkish authorities removed from the plane 12 parcels said to contain communications devices for military purposes, the newspaper said. The Turkish daily Todays Zaman said authorities also discovered components that could be used in missiles.
Turkish Foreign Minister Ahmet Davutoglu said solid intelligence had been received suggesting the plane carried illegal cargo in violation of international aviation rules.
Davutoglu said Turkey has said it won't allow military or cargo planes carrying arms to Syria to use Turkish airspace, the paper said.
Ankara warned Turkish airlines to avoid using Syrian airspace in case of possible retaliation from Damascus, NTV said.