ANKARA (Reuters) - Prime Minister Tayyip Erdogan said on Thursday Turkey could act against a "terrorist" organisation in northern Syria if it sees it as a threat, in a warning to Kurdish militants believed to be active in the region.
Erdogan's talk of possible intervention marked a new escalation in tensions between Turkey and its southern neighbour, which have been increasingly at odds since Syrian President Bashar al-Assad failed to heed Ankara's calls to quit.
"We will not allow a terrorist group to establish camps in northern Syria and threaten Turkey," Erdogan told a news conference before travelling to London.
"If there is a step which needs to be taken against the terrorist group, we will definitely take this step," he said.
His comments were Ankara's first acknowledgement of concern about the growing influence of Syria's Democratic Union Party (PYD) - linked to the Kurdistan Workers Party (PKK) which has fought a 28-year separatist conflict in Turkey in which more than 40,000 people have died.
Syria's Kurdish areas have been spared the worst of the violence in the 16-month-old revolt against Assad and Kurds are seizing the opportunity to exert their authority in the north, where the PYD has reportedly taken control of four towns.
Syrian opposition figures have accused the PYD of acting as enforcers for Assad, putting down demonstrations in Kurdish areas and assassinating anti-Assad activists.
In recent years Turkey has carried out regular attacks with air strikes and artillery fire against PKK militants based in the mountains of northern Iraq and Erdogan's comments triggered speculation about what action Turkey might take in Syria.
There has been previous talk about the creation of a buffer zone along the Syrian border and Erdogan said that was among the options which could be considered. However Turkey was not expected to act unilaterally and a U.N. resolution was unlikely given Russian opposition.
Security analyst Gareth Jenkins said PKK activity in Syria was unlikely to include armed attacks against Turkey.
"Could the PKK establish propaganda centres and carry out basic military training in the Kurdish areas of Syria? Yes. Are they likely to use it as a platform for attacks against Turkey? No. Because the terrain just isn't suitable," he said.
He said the groups associated with the PKK were currently involved in enforcing law and order and local policing.
"This is a big problem for Turkey. But Turkey can't go and bomb or invade just because the PKK are directing the traffic," Jenkins said.
Turkey has harboured Syrian rebels and tens of thousands of refugees along its border with Syria. Hostility between the two countries flared up last month when a Turkish jet was shot down by Syrian air defences.
Ankara subsequently increased its military presence, sending anti-aircraft missiles to the border and scrambling planes when Syrian aircraft came close to Turkish territory.
Erdogan said on Thursday Assad and those close to him were about to leave power and preparations were under way for a "new era" in Turkey's southern neighbour.
Assad's father, the late Hafez al-Assad, for years sheltered PKK leader Abdullah Ocalan before the threat of a Turkish invasion in 1998 forced him to send Ocalan abroad, where Turkish agents eventually captured him and brought him back to Turkey.
As Turkish-Syrian relations improved, Bashar al-Assad cooperated with Ankara by cracking down on PKK elements hunkered down in Syria, but those ties disintegrated last year after Assad deployed military forces to crush popular unrest.
Turkish Foreign Minister Ahmet Davutoglu is expected to visit the northern Iraqi region of Kurdistan next week and analysts say he could ask regional president Masoud Barzani to exert pressure on Syrian Kurds to curb PKK influence there.
Turkey has recently established closer relations with Barzani and the Kurdish regional government as it looks to build on growing business and energy stakes in northern Iraq.
More than 7,000 Syrians have fled growing economic hardship and instability for Iraq's Kurdistan, which has been autonomous since 1991 with its own provincial government and armed forces, but relies on the Baghdad central government for its budget.
A strong PKK presence in Syria, where Kurds make up around one million of the 21 million population, could also further complicate efforts to solve its intractable Kurdish problem.
During his 10 years in power, Erdogan has pushed through reforms, mainly to increase the scope for Kurdish broadcasting and teaching, designed to address the grievances of a minority of some 12 million people.
However, inspired by the example of northern Iraq, many Turkish Kurdish politicians are pushing for political autonomy. (Additional reporting by Ayla Jean Yackley; Writing by Daren Butler; Editing by Myra MacDonald)