ISTANBUL President Tayyip Erdogan said on Monday Turkey would use all its military and intelligence might to battle "one of the biggest and bloodiest terrorist waves in its history", after a suicide bomber killed three Israelis and an Iranian in Istanbul.
Israeli Defense Minister Moshe Yaalon described Turkey as "awash in terrorism". Turkey's main opposition party blamed what it called the government's "adventure-seeking policies" in the Middle East for turmoil washing across Syria's borders.
Saturday's attack on Istiklal Street, a long pedestrian avenue lined with international stores and foreign consulates, was the fourth suicide bombing in Turkey this year. Two in Istanbul have been blamed on Islamic State, while the two others in the capital Ankara have been claimed by Kurdish militants.
The attacks have raised questions at home and among NATO allies as to whether its security services are overstretched as they fight on two fronts.
"Turkey has recently been facing one of the biggest and bloodiest terrorist waves in its history ... Our state is fighting terrorist organizations and the forces behind them with everything at its disposal - its soldiers, police, village guards and its intelligence," Erdogan said in a speech in Istanbul.
But his critics, including privately some of Turkey's allies, argue that Erdogan's focus on battling Kurdistan Workers Party (PKK) militants in the largely Kurdish southeast - a campaign he has repeatedly vowed will continue - comes at the expense of its fight against Islamic State.
Erdogan said the PKK and other groups were working with Islamic State and had turned on Turkey because they had failed to achieve their aims elsewhere in the region. He accused Europe of "two-faced behavior" for allowing PKK sympathizers to set up a tent near an EU-Turkey summit in Brussels last week.
Turkey has seen phases of civil disorder, a military coup in 1960, and left-right street clashes in the 1970s and 1980s that triggered two further army interventions. The Kurdish conflict has also caused widespread bloodshed, but rarely has a Turkish government faced such serious domestic conflicts simultaneously.
Turkey is part of a U.S.-led coalition against Islamic State in Syria and Iraq, but is also fighting PKK separatists in its southeast, where it sees an upsurge in violence since July as fueled by the territorial gains of a Kurdish militia in Syria.
Israeli Defense Minister Yaalon said the roots of the violence lay in radical Islam he said was "flooding the world".
"What must be ensured is that terrorism is not initiated, like the way Hamas initiates terrorism against us, from Turkey, from Istanbul," he said in a speech, in a swipe at Ankara’s support for the Palestinian Islamist militant group, which Israel sees an obstacle to repairing bilateral ties.
Government officials deny suggestions that Turkey, long seen by Washington as a model for Islamic democracy but now facing Western criticism over its human rights policies, is not focused on fighting Islamic State.
But the main opposition Republican People's Party (CHP), which has criticized what it sees as a pro-Sunni sectarian meddling in Syria, blamed Turkish foreign policy.
"What we are going through now is the result of the (ruling) AK Party’s unstable, contradictory, utopian, adventure-seeking policies in the Middle East," CHP group deputy chairman Engin Altay told a press conference in parliament.
At least half a dozen newspapers from across the political spectrum carried head-and-shoulders pictures of three more suspected Islamic State members on Monday, saying they had been instructed to carry out further attacks in crowded areas.
"All provincial police units have taken action to try to capture the three terrorists suspected of being Islamic State members planning sensational attacks," the state-run Anadolu news agency said.
Interior Minister Efkan Ala on Sunday identified the Istanbul bomber as a Mehmet Ozturk, born in 1992 and from the southern province of Gaziantep near the Syrian border. Five people had been detained in connection with the blast.
Israel has confirmed that three of its citizens died. Two held dual citizenship with the United States. An Iranian was also killed, Turkish officials have said.
Israeli Prime Minister Benjamin Netanyahu has said Israel is trying to determine whether its citizens were deliberately targeted. Eleven of the 36 wounded were Israelis.
Turkey's Haberturk newspaper said police had been examining CCTV footage and that it appeared the suicide bomber had followed the group of Israeli tourists for several kilometers from their hotel, then waiting outside the restaurant where they ate breakfast before blowing himself up as they emerged.
Israeli media gave details of those who died.
Yonathan Suher, a father of two, had traveled to Istanbul to celebrate his 40th birthday with his wife, who was seriously wounded. Kindergarten teacher Simcha Damari, 60, and Avi Goldman, 63, who worked as a tour guide in Israel, both left behind several grandchildren, Israeli media said.
(Additional reporting by Daren Butler in Istanbul, Gulsen Solaker in Ankara, Dan Williams in Jerusalem; Writing by Nick Tattersall; editing by Ralph Boulton)