A U.S. airstrike on Friday killed four Islamic State fighters in western Iraq, including a leader who appeared in ISIS execution videos and was considered an heir apparent to terror mastermind Abu Musab al-Zarqawi, the Pentagon announced Monday.

The terror leader, Abu Wahib, was known as the "Emir of Anbar Province." The strike unfolded near al-Rutba, not far from the Syrian border, Pentagon Press Secretary Peter Cook told reporters.

Wahib left an Anbar university, where he was studying computer science, to fight U.S. forces entering Iraq, The New York Times reported. He escaped from an Iraq-run prison in Tikrit in 2012.

Cook said Wahib's death marks another serious blow to ISIS leadership and would "further degrade its ability to operate, especially in Anbar Province."

Iraq had falsely reported Wahib's death in the past, but Cook said, "we're confident that this was a successful strike and I'll leave it at that."

He said it was part of U.S. efforts to put pressure on terror leaders in as many different ways as possible, signaling they should be "very worried about their next step."

U.S. and Iraqi officials said an airstrike killed Zarqawi outside Baghdad in 2006.

Fox News' Lucas Tomlinson contributed to this report.