* Turkish fighter planes escort Syrian plane to airport
* Foreign minister says plane to be free if nothing on board
By Gulsen Solaker
ANKARA, Oct 10 (Reuters) - Turkey forced a Syrian passenger plane en route from Moscow to Damascus to land in Ankara on Wednesday on suspicion that it was carrying military equipment destined for Syrian President Bashar al-Assad's forces, Turkey's foreign minister said.
Turkish fighter planes escorted the Syrian plane, which was carrying around 30 passengers, into the airport in Ankara after Turkish authorities received information that it was carrying "non-civilian" cargo which had not been registered.
"We are determined to control weapons transfers to a regime that carries out such brutal massacres against civilians. It is unacceptable that such a transfer is made using our airspace," Turkish Foreign Minister Ahmet Davutoglu said.
"Today we received information that this plane was carrying cargo of a nature that could not possibly be in compliance with the rules of civil aviation," he said on Turkish television.
Tensions between Turkey and Syria, once close allies, have become increasingly strained during the rebellion in Syria against President Bashar al-Assad.
Davutoglu said Turkey was within its rights to investigate planes suspected to be carrying military materials and that the plane would be allowed to continue if it was found to be clean. He declined to comment on what the banned materials might be.
He said Turkey would continue to investigate Syrian civilian aircraft using its airspace.
He also said Syrian air space was no longer safe and that Turkish passenger planes should not fly there. A Reuters witness at the border saw at least one passenger plane turn around as it approached Syria and head back into Turkey on Wednesday.
Turkey's armed forces have bolstered their presence along the 900-km (560-mile) border and have been firing back over the past week in response to gunfire and shelling coming from northern Syria, where Assad's forces have been battling rebels who control swathes of territory.
The Syrian government has made heavy use of air power and artillery to halt rebel advances in the conflict, now in its 19th month.