France's foreign minister says his government is working to spare four French former members of the Islamic State group from execution after Iraq sentenced them to death.

However, France has made no effort to bring back captured French IS fighters, including the four sentenced this week.

Foreign Minister Jean-Yves Le Drian reiterated France's position on Tuesday, saying the four terrorists should be tried where they committed their crimes.

But he said on France-Inter radio that "we are multiplying efforts to avoid the death penalty for these four French people."

He didn't elaborate, but said he spoke to Iraq's president about the case. France is outspoken against the death penalty globally.

There's been controversy about the legal treatment of thousands of foreign fighters who joined IS in Syria and Iraq.