(JTA) — The Turkish government of Prime Minister Recep Tayyip Erdogan divulged to Iran the identities of as many as 10 Iranian spies for Israel who met with their Mossad handlers in Turkey, according to the Washington Post.

David Ignatius, an Opinion writer for the newspaper, disclosed the incident in a column published Thursday. He said it occurred last year and is now being reported for the first time.

Ignatius cited what he called knowledgeable sources as saying the leak was a “significant” loss of intelligence and “an effort to slap the Israelis.”

The incident, Ignatius said, could explain why Israeli Prime Minister Benjamin Netanyahu was “so entrenched” in his refusal to meet Turkey’s demand of apologizing for the Mavi Marmara incident of May 2010, in which nine Turkish citizens were killed when Israeli naval commandos boarded a ship attempting to break Israel’s naval blockade of the Gaza Strip.

Netanyahu spoke by phone to Erdogan in March when he offered an American-brokered apology to the Turkish prime minister.

Ignatius said the United States did not protest the exposure of such a great intelligence loss to Turkish officials, choosing instead to continue to work on warming Turkish-American relations. He said U.S. officials are not sure whether the intelligence exposure was in retaliation for the Gaza flotilla attack or just a sign of deteriorating relations between Turkey and Israel.

Israel, which Ignatius said has been cooperating with Turkish intelligence in secret for more than 50 years, does not trust Turkish intelligence chief Hakan Fidan because of his ties with Iran, even as the United States deals with him on sensitive matters, according to Ignatius.

Fidan allegedly passed to Iran sensitive intelligence collected by the U.S. and Israel, The Wall Street Journal reported recently.