Russian officials say a Turkish jet recently shot down by Damascus entered Syrian airspace twice to test the country’s anti-aircraft defenses.

The Interfax news agency cited an unnamed senior member of Russia’s military who said the Turkish F4 Phantom’s June 22 mission had been to gauge the combat readiness of Syrian air defenses.

“It was a clear provocation,” the official was quoted as saying,

The official also said that Russian security officials believe the F4 had also been gathering intelligence on Syrian land and shore defenses.

Russian Foreign Minister Sergei Lavrov, in recent comments, said Russia’s military intelligence had monitored the flight and the shoot down.

Moscow has billions of dollars in military, oil, and infrastructure contracts tied to the survival of embattled Syrian president Bashar al-Assad.

To that end, Russian officials have used their Security Council veto to shield Damascus from international furor and action at the United Nations.

Relations between Ankara and Damascus, once allies, have soured during Assad’s brutal 16-month crackdown on a popular uprising against his 11-year rule.

However, the June 22 incident has served as a fulcrum of tension between Turkey and Syria, with both nations deploying military forces, including combat aircraft, on their mutual frontier since the F4 was shot down.

Ankara, which has absorbed thousands of refugees from Syria in recent months, has also given safe haven to the senior commanders of the rebel Free Syrian Army.

Rights groups say at least 16,500 people – most of them civilians – have been killed in the unrest-turned-civil-war now gripping Syria.