Turkey's president has said his country will take "necessary" but unspecified action against Syria, a day after Damascus said it had brought down a Turkish military plane that had entered its airspace.
Abdullah Gul said that Turkey was still trying to establish the exact circumstances of the incident and whether the jet may have been brought down in Turkish territory.
The plane went down in the Mediterranean Sea about eight miles away from the Syrian town of Latakia, Turkey said.
The incident further escalated tensions between the two neighbours, which used to be allies before the Syrian revolt began in March 2011. Turkey has become one of the strongest critics of the Syrian regime's brutal response to the country's uprising.
Turkish media said that Syrian and Turkish coastguards are conducting a joint search mission for the jet's two missing crew members.
"No cover-up is possible," the state-run Anadolu Agency quoted Mr Gul as saying. "There is no doubt that the necessary steps will be taken."
Mr Gul did not elaborate on what those steps would be.
"Our investigation will focus on whether the plane was brought down within our borders or not," Mr Gul said. "Because the consequences could be quite serious, there will be no clear statement before the details (of the incident) are scrutinised."
The Turkish president added that it was "routine" for jets flying in high-speeds to violate other countries' airspaces for short periods of time.
Late on Friday, Syria's state-run news agency, SANA, said the military spotted an "unidentified aerial target" that was flying at a low altitude and at a high speed.