MOSCOW — The leaders of Turkey and Russia flung insults at each other on Thursday in their deepening feud over the shooting down of a Russian warplane, with President Vladimir V. Putin warning that Moscow would do more than merely ban tomatoes and construction projects to penalize Ankara.

The Kremlin also said that the long-delayed transfer of the S-300 air defense system to Iran had started, a move that strengthens one of Turkey’s regional rivals while raising concerns in Israel.

The foreign ministers of Russia and Turkey met on Thursday in Belgrade, Serbia, on the sidelines of a conference of the Organization for Security and Cooperation in Europe. Given the general mood in the ministers’ home countries, however, the tension persisted.

In Moscow, Mr. Putin, delivering his annual speech on the state of the federation, opened by repeating his call for an international coalition to fight terrorism and then suggested that the Turkish leadership was deranged. For his part, the Turkish prime minister, Ahmet Davutoglu, accused the Kremlin on Thursday of practicing a crude, “Soviet-style propaganda.”