The first batch was delivered even after repeated US calls on Turkey to cancel the deal or face punishment, Presstv Reported.
Russia and Turkey finalized an agreement on the delivery of the advanced defense systems in December 2017.
The latest developments come amid Washington’s threat that Turkey will be subjected to sanctions when the Russian air defense missile systems are actually delivered to its NATO ally.
Turkey and the US have been at loggerheads over the systems, which Washington claims are not compatible with the defenses of the NATO military alliance and could compromise F-35 fighter jets, being delivered to Ankara and built with Turkish help.
Amid the deliveries of the S-400 systems, Washington has begun the process of formally expelling Turkey from the program for developing F-35s, built by Lockheed Martin Corp.
Turkish President Recep Tayyip Erdogan recently described US refusal to deliver the F-35 stealth fighters to Ankara as “robbery” on a visit to China.
The Turkish president said his country had so far paid 1.4 billion dollars for the F-35s and received only four out of 116 jets.
Turkish Foreign Minister Mevlut Cavusoglu has said his country will take retaliatory measures in case the United States imposes sanctions on Ankara over its acquisition of the S-400 missile defense systems.
Turkish officials, however, said on Thursday that Turkey's removal from the F-35 jet program is not finalized and Ankara only remains suspended for now. They said it is unclear whether Turkey will be refunded for its investments in the project.
Russian state corporation Rostec has said Moscow is ready to supply its Sukhoi Su-35 jets to Turkey if Ankara demands them.
The S-400 entered service with the Russian army in 2007 and is considered the country's most advanced long-range anti-aircraft missile system.
Capable of engaging targets at a distance of 400 kilometers (248 miles) and at an altitude of up to 30 kilometers (18 miles), the missile system can destroy aircraft as well as cruise and ballistic missiles. It can also be used against land-based targets.
Several countries have finalized contracts with Moscow on the purchase of the military equipment in recent years.
Russia’s Tass News Agency quoted an unnamed military source as saying on Wednesday that Russia had begun delivering the 2nd batch of its advanced S-400 missile defense systems to China as part of a 2014 contract.
In September last year, India also approved a plan to purchase five Russian-built S-400 defense systems, despite earlier warnings from the US against any military transaction with Russia.