Turkish intelligence agents brought 49 hostages seized by the Islamic State group (IS) in northern Iraq back to Turkey on Saturday after more than three months in captivity, in what President Tayyip Erdogan described as a covert rescue operation.

The hostages, including Turkey’s consul-general, diplomats’ children and special forces soldiers, were brought to the southern Turkish city of Sanliurfa in the early hours of the morning. Police formed a cordon outside the airport as they arrived in buses with curtains drawn, a Reuters witness said.

Prime Minister Ahmet Davutoglu said he was returning from an official visit to Azerbaijan to meet the group and would take them by plane to the capital Ankara.

“I thank the prime minister and his colleagues for the pre-planned, carefully calculated and secretly-conducted operation throughout the night,” Erdogan said in a statement.

“MIT (the Turkish intelligence agency) has followed the situation very sensitively and patiently since the beginning and, as a result, conducted a successful rescue operation.”

Speaking to reporters in Azerbaijan, Davutoglu declined to give details on the circumstances of the hostages’ release.

“This was a procedure carried out through MIT’s own methods. This work had intensified in recent days,” he said in comments broadcast by Turkey’s state-run TRT television.

The group was seized from the Turkish consulate in Mosul on June 11 during a lightning advance by IS insurgents. Turkish officials had repeatedly said efforts were underway to secure their release and that the hostages were in good health but had declined to comment further.

Security sources said they were released on the Syrian side of the border with Turkey after travelling from the eastern Syrian city of Raqqa, IS’s stronghold.

Their capture had left Turkey, a member of the NATO military alliance and a key US ally in the Middle East, hamstrung in its response to the Sunni insurgents, who have carved out a self-proclaimed caliphate in parts of eastern Syria and western Iraq, just over the Turkish border.

Turkey hesitates on military action in Iraq

The rapid and brutal advance of IS, bent on establishing a hub of jihadism in the centre of the Arab world and on Turkey’s southern fringe, has alarmed Ankara and its Western allies, forcing them to step up intelligence sharing and tighten security cooperation.

The United States is drawing up plans for military action in Syria against IS fighters, but Turkey had made clear it did not want to take a frontline role, partly because of fears for the fate of the hostages.