Britain's Sky News quoted intelligence sources on Monday as saying that Islamic State had "advanced plans" to kill Jewish children in Turkey by attacking kindergartens, schools and youth centers.
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Sky foreign affairs editor Sam Kiley said the information on the "imminent" threat came from six operatives arrested over the past week in the southern Turkish city of Gaziantep.
It was not clear which country's intelligence service had provided the information to the British news network. Reuters could not verify the report and Turkish officials were not immediately reachable for comment.
"In light of these circumstances, extraordinary security measures are being taken above and beyond the high alert level already in place by the Turkish police, as well as vigilance within the Jewish community," Sky quoted an intelligence source as saying on its website.
"Undercover and other covert counter-terror measures are being implemented around the clock. This is a more than credible threat. This is an active plot," the source was quoted as saying.
More than 80 people have been killed in a series of suicide attacks this year in Turkey, a NATO ally of the United States. The latest attack, blamed on Islamic State, killed three Israeli tourists and an Iranian in Istanbul on March 19. The group has also claimed responsibility for suicide blasts that killed 35 people last week in Belgium.
In an upgraded travel advisory on Monday, Israel urged its citizens visiting Turkey to leave "as soon as possible," predicting possible follow-up attacks.
Sky said the most likely target of an attack was a synagogue in Istanbul's Beyoglu district which has a community center and a school attached to it.