By Ankara correspondent Chris Morris

Since Abdullah Ocalan was sentenced to death last week, the PKK rebel movement has been sending out a blunt message: violence is still an option.

Rebel spokesmen have said the conflict could well spread. It seems fairly obvious that there is disagreement within the movement between moderates, who support their leader's call for peace, and hardliners, who believe violence is their only weapon.

Local media in Turkey, quoting security sources, have reported that a number of PKK bomb experts have been sent into urban areas, although the PKK has never really been an urban organisation.

Its strength is fighting in the mountains. It's still not clear whether it has the ability to carry out a sustained campaign of violence in Turkey's main cities.

But small scale and isolated acts of terror are certainly a possibility and that's what's been developing over the last few days.

It mirrors the initial reaction of the PKK after Abdullah Ocalan was captured in February.

There have already been a number of arrests as the security forces go on high alert.

Many Turkish analysts argue that the more militant wing of the PKK would now welcome Mr Ocalan's execution.