Turkey is allowing Hamas to plan attacks on Israel from Istanbul, according to a report in the Daily Telegraph on Wednesday.
An attempt to assassinate Jerusalem Mayor Nir Barkat earlier this year had been one of the operations plotted from Turkish soil, the paper said.
Both Turkey and Hamas denied the allegations, which are based on transcripts of Israeli police interrogations of suspects.
But an Israeli foreign ministry spokesman said: “Israel is extremely concerned that Turkey is allowing Hamas terrorists to operate from its territory, in planning and engaging in terrorist attacks against Israeli civilians.”