Turkey and Russia are on the same page regarding the territorial integrity of both Iraq and Syria, President Recep Tayyip Erdoğan said Thursday at a joint press conference with Russian President Vladimir Putin.

The two leaders held a meeting at the Presidential Palace complex in Ankara, which lasted for about three hours. Speaking to the press after the meeting, Erdoğan said that regional issues, including the latest developments in Syria and the Kurdistan Regional Government's (KRG) controversial independence referendum were discussed.

"We need to protect the Iraqi central government in order to assist them in safeguarding the country's sovereignty," Erdoğan said. He also said that Turkey and Russia agreed to cooperate closely to solve the Syrian crisis through diplomacy, adding that he is happy with the progress made in the Astana process, sponsored by Turkey, Russia and Iran.

He stressed that Ankara and Moscow are "committed to a political solution to the Syrian crisis."

Putin praised Erdoğan for his efforts and initiative to establish de-escalation zones in Syria, saying they "have de-facto created the necessary conditions for the end of the fratricidal war in Syria and the final defeat of terrorists … for the Syrian people's return to normal life."

Putin contended that the establishment of de-escalation zones in Syria had given significant momentum to the Geneva process, referring to the peace talks between the Syrian regime and opposition representatives.

"It was really difficult to carry out the working of these de-escalation zones," Putin said, adding that an important achievement had been made thanks to Erdoğan.

Meanwhile, Russian presidential aide for military and technical cooperation Vladimir Kozhin said on Friday that the contract to supply Russian S-400 missile systems to Turkey is being fulfilled and Ankara has already made the down payment, TASS agency reported.

"The contract has entered into force, the advance payment has been made, I cannot say about the timeframe now," Kozhin said.

Turkey's request for joint production of the S-400 systems has not been discussed and the parties have agreed only on the supply of produced systems, he added. "We are not speaking about it, as yet we speak only about supplies of ready weapons, technologies," Kozhin said.

Previously this month, Erdoğan said that Turkey's purchase of S-400 missile systems from Russia was a done deal, with the down payment already having been transferred to Moscow.

The two leaders also discussed bilateral trade relations and the increasing flow of Russian tourists to Turkey.

Erdoğan said Ankara is pleased that the trade volume between the two countries has risen by 22 percent so far this year, reiterating that Turkey and Russia aim to reach $100 billion in trade in the near future.

Putin, in turn, said that exports of Turkish agricultural products to Russia increased 58 percent in the first half of 2017, citing the lifting of restrictions as a reason for the rise.

"The number of Russian tourists visiting Turkey this year rose 11 times, reaching more than 2.5 million people," Putin said, adding that it was due to a series of high-level talks and consultations between officials of the two countries.

After Turkey shot down a Russian military jet over an airspace violation in November 2015, Moscow took several measures against Ankara, including banning imports of Turkish agricultural products and ending visa-free travel for Turkish citizens.

Since last summer, Russia has relaxed the measures and lifted bans on some products, particularly citrus.

During a May 3 visit to Russia, Erdoğan and Putin had agreed to resumef trade, including food and textiles, but with the exception of tomatoes.