Turkey has received the first parts of a Russian S-400 missile defence system despite opposition from the US.
The shipment arrived in an airbase in the capital Ankara on Friday, the Turkish defence ministry says.
The move will anger the US, which has warned that Turkey cannot have both the S-400 anti-aircraft defence system and US F-35 fighter jets.
Turkey and the US are Nato allies – but Turkey has also been establishing closer links with Russia.
A Nato official told the AFP news agency that the body was “concerned” about Turkey’s acquisition.