Turkey has sacked a top defence official who had been involved in negotiations over a multi-billion-dollar missile deal with a Chinese firm, media said Friday.

Murad Bayar, who had been the secretary of state for defence industries for 10 years, was sacked with immediate effect, the Anatolia news agency said, citing the official gazette but without stating the reason.

Bayar had been a key player in negotiations to buy Turkey's first long-range anti-missile system with the defence contractor China Precision Machinery Export-Import Corp -- a deal estimated to be worth $4 billion (2.9 billion euros).

The United States had voiced concern over Turkey's decision to enter talks with the company, which is currently subject to US sanctions for selling arms and missile technology to Iran and Syria.

The potential deal also provoked concern at NATO, which said missile systems within the transatlantic alliance must be compatible.

Turkey, a NATO member since 1952, defended its decision to enter into negotiations with the company, saying the Chinese firm had offered the most competitive price, as well as co-production in Turkey and the option of a technology transfer.