Ankara, Jul 15 (IANS): Delivery of the Russian S-400 defence missile system to Turkey continued on Monday, as an eighth Russian plane carrying equipment of the system landed at an airbase near capital Ankara, the Turkish Defence Ministry said.

"Delivery of parts of the S-400 Long Range Air and Missile Defence Systems is continuing. In this context, the eighth plane landed at Mürted Airbase," The Hurriyet Daily newspaper quoted the Minister as sayingin a Twitter post.

Deliveries of Russia's S-400 missile systems to Turkey began on July 12. According to the Ministrye, on that day three cargo planes delivered several truck tractors and a transport and load vehicle for S-400 systems to Murted Air Base, reports Russia's state-run TASS news agency.

Another Russian plane arrived the next day. On Sunday, Turkey confirmed the arrival of the seventh plane.

On July 14, Turkish President Recep Tayyip Erdogan described the S-400 deal with Russia as a major agreement in Ankara's modern history.

He noted that the supplies of Russia's air defence systems could be completed by April 2020.

In December 2017, Ankara and Moscow signed a $2.5 billion agreement for two batteries of the S-400 system, Russia's most advanced long-range anti-aircraft missile system.

Turkey is the first NATO member country to acquire the system, Xinhua news agency reported.

Ankara's cooperation with Russia on this missile system has been strongly criticized by Turkey's NATO ally, the US.

In April, the Pentagon claimed that Turkey's adoption of Russian missile could cause security risk on F-35 jets and NATO defence system.

US President Donald Trump's administration has also threatened to impose severe sanctions on Turkey if the S-400 missiles deal with Moscow was followed through.

However, Turkey has refused to bow to US pressure, insisting that choosing which equipment to purchase is a matter of national sovereignty and does not target any third country.