Turkey jailed 17 suspects on Tuesday, mostly foreigners, over last week's suicide bombing at Istanbul's main airport, which President Tayyip Erdogan described as the work of Islamic State militants from the ex-Soviet Union.
The arrests bring the total number of people jailed pending trial to 30 over the triple suicide bombing at Ataturk Airport, which killed 45 people and wounded hundreds, the deadliest in a series of bombings this year in Turkey.
It was followed by major attacks in Bangladesh, Iraq and Saudi Arabia in the past week, all apparently timed for the runup to Eid al-Fitr, the holiday marking the end of the Ramadan holy fasting month.
"The incident is of course completely within the framework of Daesh, a process conducted with their methods," Erdogan told reporters after praying at an Istanbul mosque at the start of the holiday. Daesh is an Arabic acronym for Islamic State.
Three bombers opened fire to create panic outside the airport before two of them got inside and blew themselves up.
The third militant detonated his explosives outside at the entrance to the international arrivals terminal.
"There are people from Dagestan, from Kyrgyzstan, from Tajikistan," Erdogan said, referring to a mainly Muslim province of Russia's North Caucasus region, and two former Soviet states in Central Asia. "Unfortunately, people from neighboring northern Caucasus countries are involved in this business."
The 17 remanded in custody early on Tuesday included 11 foreigners. All were accused of "membership of an armed terrorist organization", the private Dogan news agency said.
Thirteen others were jailed on Sunday, including three foreigners.
The state-run Andolu news agency said last week that two of the bombers were Russian nationals. One government official has said the attackers were Russian, Uzbek and Kyrgyz nationals.
Moscow says that thousands of Russian citizens and citizens of other former Soviet states have joined Islamic State, travelling through Turkey to reach Syria. Russia fought two wars against Chechen separatists in the North Causcasus in the 1990s, and more recently has fought Islamist insurgents in Dagestan.
Russia and Turkey have been at odds over Moscow's support for Syrian President Bashar al-Assad and Turkey's backing of rebels opposed to him, especially since last year when Turkey shot down a Russian warplane near the border.
But recent weeks have seen a thaw in relations between the two countries, with both citing a need to bury their differences to fight the common Islamic State foe.
The pro-government Yeni Safak newspaper has said the organiser of the attack was suspected to be a Chechen double-amputee called Akhmed Chatayev. He is identified on a United Nations sanctions list as an Islamic State leader responsible for training Russian-speaking militants.
Suspects deny allegations
During questioning in court, as reported by Dogan, the suspects denied links to the bombers.
One of them, identified as a Russian citizen named as Smail A., said he stayed in a crowded house where he thought he would be able to read the Koran.
"When the police caught us they said terrorists had stayed there previously, but we didn't know. I was in that house at the wrong time," he was quoted as saying during questioning.
A suspect identified as Kamil D., also a Russian citizen, denied knowing one of the bombers, who has been identified as Rahim Bulgarov.
"The people constantly changed in the house where we stayed. Maybe he came and stayed but I don't know him," he said.
A third suspect, Turkish citizen Cengizhan C., said he embraced the views of Islamic State after following related groups on Facebook.
"I learned Daesh ideas. I bonded with them idea-wise. I believed what they stood for," he said, adding he traveled to the border province of Sanliurfa with the aim of joining them in Syria but had been dissuaded from doing so.
In the wake of the attack, Turkey has beefed up security at airports and train stations, Prime Minister Binali Yildirim said on Monday ahead Eid al-Fitr, which continues until Thursday.
Turkey is a member of a U.S.-led coalition fighting against Islamic State. It also faces a separate security threat from a Kurdish insurgency in its largely Kurdish southeast.