UNITED NATIONS (REUTERS) - UN Secretary-General Ban Ki-moon on Wednesday urged the Islamic State in Iraq and Syria captors of a Jordanian pilot whose warplane was shot down in north-east Syria to treat him humanely, his spokesman said.

"He (Ban) calls on his captors to treat the pilot in accordance with international humanitarian law," UN spokesman Stephane Dujarric said.

The pilot is the first captive taken from the US-led coalition carrying out air strikes against the militant group that has seized parts of Syria and Iraq.

He told reporters that Ban was also "deeply concerned with the continued use of violence across the country, including the use of 'barrel bombs' in populated areas."

Dujarric noted that the indiscriminate use of such weapons was a violation of international law.