The Jordanian army on Wednesday confirmed that one of its warplanes was shot down in Syria and its pilot captured by ISIL.
The militant group said that its fighters had shot down a military jet and captured pilot Moaz al-Kasasba in the city of Raqqa.
"[Ban Ki-moon] calls on his captors to treat the pilot in accordance with international humanitarian law," said Stephane Dujarric, his spokesman.
ISIL-held Raqqa has been targeted several times by an international coalition led by the U.S.
"The secretary-general is deeply concerned with the continued use of violence across the country including the use of barrel bombs in populated areas," he said.
The conflict in Syria that began in March 2011 has claimed nearly 200,000 lives and as many as 12.2 million people now require humanitarian assistance, according to the UN.
The unrest created by the civil war paved the way for extremist movements such as ISIL to gain a foothold in the region.
The group captured Iraq's second city of Mosul in June and then surged across large swathes of land in northern Iraq and Syria, taking control of a number of predominantly Sunni cities.