The event is also being attended by U.S. Secretary of State John Kerry, Russian Foreign Minister Sergey Lavrov, EU foreign policy chief Federica Mogherini. Council of Europe Secretary General Thorbjorn Jagland.
The plenary session was opened by the OSCE chairman, Serbian Foreign Minister Ivica Dacic, and the welcome speech was delivered by Serbian Prime Minister Aleksandar Vucic who said that because of its history Serbia knew how to appreciate peace more than other countries.
"Serbia's priorities today are peace and security, we want to leave the past behind ... and look to the future with our eyes wide open," Vucic said.
He said that terrorism and extremism posed a serious threat to the contemporary world, calling for wiping out divisions and for unity in the fight against terrorism.
A number of bilateral meetings were held on the fringes of the summit and over 100 such meetings have been announced for Thursday alone. After a recent incident when Turkey took down a Russian combat aircraft at its border with Syria, a possible meeting between Turkish Foreign Minister Mevlut Cavusoglu and Russian foreign policy chief Lavrov will definitely be in the limelight.
The Russian news agency RIA cited unnamed sources as saying that Lavrov and Cavusoglu would meet in Belgrade, without revealing more details.
Secretary general in the Serbian Foreign Ministry Veljko Odalovic told Radio Television Serbia that "conditions have been created for the meeting between Lavrov and Cavusoglu , but that this does not depend on Serbia."
After arriving in Belgrade on Wednesday, Lavrov told the press he was prepared to meet his Turkish counterpart on the margins of the summit because Moscow wanted to have Turkey's position clarified.
Relations between Ankara and Moscow have deteriorated since November 24 when a Russian warplane was shot down by a Turkish F16 near the border with Syria, killing one of the pilots.
Ankara says that the plane was shot down after it illegally entered Turkish airspace. Russia insists the aircraft was above Syrian territory.
Let us hear what the Turks want to say, besides what they already have said. It will be sad if they have nothing new to say, Lavrov told a news conference which he held together with Serbian Foreign Minister Dacic. Lavrov underscored that Russia had some questions for Turkey.
The summit is Belgrade is held under heave security measures, which have additionally been stepped up following recent terror attacks in Paris and tensions on the international political scene following the Turkey-Russia incident.