Separately, fighting in southeastern Turkey killed three soldiers and three Kurdistan Workers Party (PKK) rebels late on Thursday, another official said.
Syrian police detained the PKK's Hamili Yildirim, who has evaded capture since 1996, and the others in July as they tried to cross into Turkey from Syria, a police official said.
They were based in a PKK stronghold in northern Iraq and were heading for the Turkish city of Tunceli, where separatist violence has been on the rise, newspapers said.
Turkish police have been interrogating the men in a prison in Hatay province, bordering Syria, since taking them into custody on 4 September after weeks of talks with Syria, the official said.
Diplomatic and commercial ties between the neighbours have improved considerably since a low point in 1998, when Turkey threatened to invade its smaller Arab neighbour if it did not
Ties between Syrian and Turkey
improved after Ocalan's expulsion
expel PKK leader Abd Allah Ocalan.
Ocalan had led the PKK's armed campaign for an ethnic homeland in southeastern Turkey since 1984. More than 30,000 people, mainly Kurds, have died in the conflict.
Turkey captured and convicted Ocalan the following year and violence dropped sharply. But fighting has increased since the PKK called off a unilateral, six-year ceasefire in June.
Besides improved trade links and efforts to improve cultural ties, Ankara and Damascus are also united by fears the conflict in Iraq will encourage Iraqi Kurds to secede, stoking separatism among their own restive Kurdish minorities.
Intense fighting in the mountainous district of Pervari in Siirt province that broke out on Thursday is just the latest in an upsurge of violence since the PKK said it would once again
target Turkish interests.
Three soldiers and four rebels were killed after clashes broke out, a security official said.
Syria and Turkey fear the Iraq
conflict could stoke separatism
About 1000 security forces backed by helicopter gunships
were continuing operations against 100 fighters, he said.
"Operations backed by air support are continuing. There is a large number of PKK in the region. We are expanding our operation to target them," he said.