Turkish police have detained 12 people in Istanbul suspected of providing support to al Qaeda militants fighting Nato forces in Afghanistan, a senior security official said.
The detentions come just days after four men were arrested in west and southwest Turkey on suspicion of fundraising for militants and a fifth on suspicion of designing computer programmes to jam the controls of drone aircraft.
Istanbul police declined to comment.
Turkish police often arrest suspected Islamist militants and describe them as having links to al Qaeda, though details seldom emerge. Around 120 al Qaeda suspects were rounded up last January in raids mostly carried out in the southeast.
Of the five arrested last week the four suspected of fundraising have since been released pending trial.
The number of Turks fighting in the Afghanistan-Pakistan region is believed to be relatively small, though a senior security official in northwest Pakistan has told Reuters that there has been an increase over the past year.
Turks have until now played little part in al Qaeda's global jihad, but security analysts have noted an increase in the number of Turkish language jihadi websites, some of which have posted obituaries for Turkish militants killed in Afghanistan.
A Nato member, with troops serving in non-combat roles in Afghanistan, Turkey has itself been a venue for al Qaeda attacks in the past.
Graduates of bin Laden's training camps were behind the bomb attacks in 2003 that killed 57 people and wounded hundreds in Istanbul, alerting the government to the need to monitor any rise in the number of Turks going to Pakistan and Afghanistan.
Reuters