Russian Special Envoy for Syria Alexander Lavrentiev made the remarks while reading a joint statement issued by representatives of the three countries on Tuesday at the end of the tenth round of the two-day International Meeting on Syria in the Black Sea resort of Sochi.
"The Islamic Republic of Iran, the Russian Federation and the Republic of Turkey confirmed their strong adherence to the sovereignty, independence, unity, and territorial integrity of Syria," Lavrentiev said.
He added that the sides reaffirmed their determination to continue the combat against terrorism in Syria in order to completely eradicate terrorist groups, including Daesh and al-Nusra Front, and other people, groups, companies and organizations relating to al-Qaeda or Daesh and which the UN Security Council recognizes as such.
The Russian diplomat said the parties would continue to make joint efforts to promote a process of political settlement which is led and implemented by Syrians themselves in order to establish conditions that facilitate the early work of a constitutional committee in Geneva.
Iran, Turkey and Russia called on the international community, especially the UN and its humanitarian agencies, to increase assistance to Syria, restore life support facilities and social-economic infrastructure as well as preserve historic heritage, Lavrentiev added.
He noted that the three countries started discussions in coordination with the international community, United Nations High Commissioner for Refugees and other related international organizations in order to establish due conditions for the early voluntary and safe return of internally displaced people and refugees to their homes in Syria.
The Russian envoy said Tehran, Moscow and Ankara would make joint efforts in order to strengthen trust between conflicting sides in Syria, including in a framework of the working group on the release of detainees/abductees and handover of bodies, as well as the identification of missing persons with the participation of UN experts and the International Committee of the Red Cross.
Lavrentiev further added, "The parties have decided to hold the next international high-level meeting on Syria in November 2018."
UN envoy plans talks with Iran, Russia, Turkey on new Syria constitution
The UN peace envoy for Syria, Staffan de Mistura, also said on Tuesday that he plans to host Iran, Russia and Turkey for talks in September on finalizing a committee to write a new Syrian constitution.
"The special envoy looks forward to holding formal consultations with the Islamic Republic of Iran, the Russian Federation and the Republic of Turkey, very early in September in Geneva, in order to begin to finalize the constitutional committee," de Mistura's office said in a statement.
Turkey, Iran and Russia are the guarantors of a countrywide ceasefire in Syria. The three have been mediating a peace process since January 2016 among Syria’s warring sides in Astana, Kazakhstan.
Syria has been gripped by foreign-backed militancy since March 2011. The Syrian government says the Israeli regime and its Western and regional allies are aiding Takfiri terrorist groups wreaking havoc in the country.
More than 350,000 people have been killed and millions displaced since the beginning of Syria's war.