Syrian naval forces have joined Turkish rescue crews to hunt for the pilots of a Turkish Phantom F-4 reconnaissance jet, which was shot down over Syrian territorial waters on Friday.

Turkey has pledged firm action over the incident, which highlights the rapidly deteriorating relations between the once close neighbours.

President Assad's regime previously counted the vast country one of its closest friends, however, Turkey has become increasingly critical of the government, taking in thousands of Syrian refugees.

Although the situation is thought to be dire, experts do not anticipate any military retaliation without approval from Washington, which is unlikely to be forthcoming.

Turkish Armed Forces stated Friday afternoon that a military jet on a scouting mission went missing, having lost radio and radar contact near Hatay, Turkey.

Syrian state television reported that the plane was hit after passing "fast and low" through territorial waters. Turkey has said in response that its aircraft routinely pass through foreign territory en-route back to their airfields.

After the F-4 jet allegedly crashed into Syrian water, both Turkish and Syrian coastal guards started a co-operative effort to reach the two pilots.