ANKARA (Reuters) - Syrian President Bashar al-Assad has created a "terrorist state", Turkish Prime Minister Tayyip Erdogan said on Wednesday, accusing the outside world of indifference which was adding to the massacres there.
Erdogan for years cultivated good relations with Assad, but after the Syrian uprising began 17 months ago, became one of his harshest critics. The Turkish leader has long called for Assad to step down, but his latest comments were some of his strongest yet.
"The massacres in Syria that gain strength from the international community's indifference are continuing to increase," Erdogan told a meeting of his ruling AK Party.
"The regime in Syria has now become a terrorist state."
Turkey says it is struggling to cope with an influx of around 80,000 Syrian refugees and is pushing for a foreign-protected safe zone inside Syria.
But the proposal has gained little international support and Ankara has become increasingly vocal in its frustration at the U.N. Security Council and its failure to take concerted action.
At the same time, Turkey, with some half a million men under arms, appears so far unwilling to act without international support. Erdogan said Turkey could not afford to remain silent.
"For the Syrian people, Turkey is not an ordinary country. We are a country with a 910 kilometer border and tied by relatives," Erdogan said.
"For Syria, we are not the USA, nor are we England, nor Iran, nor Russia. A country in Asia can remain indifferent over Syria, but Turkey does not have that luxury," he said.
Turkish tanks conducted exercises along the border with Syria on Wednesday, a clear warning to Damascus. The exercise was the most "comprehensive" of its kind recently, state-run Anatolia news agency said, and involved maneuver and attack drills which could be seen from inside Syria.
Aside from the influx of refugees, Ankara is also concerned the crisis in Syria has emboldened separatist Kurdish insurgents within Turkey and has accused Assad of arming them.
Turkey has raised the possibility of military intervention in Syria if the Kurdistan Workers Party (PKK), which has fought in southeastern Turkey for almost three decades, were to launch attacks from Syrian soil.
"Opposing us is a sub-contractor organization without any humane values, which does not recognize anything holy and which strikes from behind in a cowardly way," Erdogan said referring to the PKK.
"This group is directly supported abroad by enemy countries," he said, hinting at Syria.
Turkey, the United States and the European Union all list the PKK as a terrorist organization.
Editing by Nick Tattersall and Jon Hemming