A Turkish soldier prays during the burial ceremony of a comrade in Gaziantep.

A Turkish soldier who went missing this week on the border with Syrian territory controlled by ISIS has been seen in a hospital run by the militants, Hurriyet newspaper reported on Saturday.

If confirmed, the soldier’s capture would be a major problem for Turkey, after it stepped up military action against ISIS in July, opening its air bases to U.S.-led coalition war planes and launching air strikes.

The soldier vanished and another was killed in cross-border shooting with ISIS fighters on Tuesday near the Turkish town of Kilis, close to Syrian territory that has been under ISIS control for months.

According to security sources citing intelligence reports, Hurriyet Daily News reported that the soldier had been wounded in the foot and was taken by militants to a hospital under their control close to the Syrian city of Aleppo.

Turkish officials declined to comment.

Late last month, Islamic State released a video accusing Turkish President Tayyip Erdogan of “treachery”, and urged Turks to rise up against him.

This would not be the first time Islamic State has held Turkish hostages. Last year 46 Turks, including senior diplomats, were kept captive for more than three months before being released.

They were freed at a time when Ankara was still being reluctant to engage in efforts to stop ISIS’s spread, a policy it changed in July.

The timing of the capture is also politically problematic for Erdogan and his AK Party, which is preparing for a second election in November after losing its parliamentary majority in a June vote.

Polls have consistently showed little appetite among Turks for greater involvement in the Middle East conflagration, and this incident will likely be leapt upon by Erdogan’s opponents, who are strongly critical of his foreign policy.