Ankara (AFP) - Turkey's F-16 jets were harassed and put on radar lock by an unidentified MIG-29 aircraft on the Syrian border, after Russian fighter planes violated Turkish airspace at the weekend, the Turkish military said on Tuesday.

"Eight Turkish F-16 jets carried out reconnaissance flights over the Turkish-Syrian border (on Monday) and during this mission our jets were held on radar lock by an unidentified MIG-29 plane for a total of four minutes and 30 seconds," the army said in a statement.

Radar lock-on enables missile systems to automatically follow a target.

In a separate incident, the same Turkish jets were also "harassed by missile systems deployed in Syria for a total of four minutes and 15 seconds," the army added.

It did not go into further detail about the nature of the harassment from the missile systems or whether the Turkish jets were in any danger.

Russian aircraft violated Turkish airspace on Saturday and on Sunday, prompting Ankara to summon the Russian envoy to the foreign ministry twice to protest the breach.

The army gave no indication that the MIG-29 was a Russian plane. It had also complained a similar incident involving an unidentified MIG-29 took place on Sunday.

In Brussels, Turkish President Recep Tayyip Erdogan warned Moscow on Tuesday against losing Turkey's friendship and said his country cannot remain "patient" in the face of air space violations.

NATO's chief Jens Stoltenberg accused Russia of deliberately violating Turkey's airspace during its air campaign on Syria.