The U.N. Security Council expressed grave concern on Monday over reports that radical militants have seized oilfields and pipelines in Syria and Iraq and warned that anyone caught trading in oil from the "terrorist groups" could face sanctions.

The 15-member council said in a statement that any trade in oil with Islamic State - previously known as the Islamic State in Iraq and the Levant - or al Qaeda's Nusra Front, would violate United Nations sanctions as both groups have been blacklisted.

The Russian-drafted statement "strongly condemns any engagement in direct or indirect trade of oil from Syria and Iraq involving terrorist groups," and "emphasizes that such engagement constitutes financial support for terrorists and may lead to further sanctions listings."

Islamic State militants seized four small oilfields when they swept through northern Iraq last month and are now selling crude oil and gasoline to finance their declared "caliphate." The group also controls oilfields in the Syrian province of Deir al-Zor after expelling the rival Nusra Front.

The Security Council "notes with concern that any oilfields and related infrastructure controlled by terrorist organizations could generate material income for terrorists, which would support their recruitment efforts, including of foreign terrorist fighters, and strengthen their operational capability to organize and carry out terrorist attacks."

It warned that all states are required to ensure that their citizens or people within their territory do no trade in oil with Islamic State or Nusra Front.