France has confirmed it will take “the necessary steps” to try to prevent Iraq carrying out the death penalty against French citizens convicted of fighting with Islamic State.

“France is opposed in principle to the death penalty at all times and in all places,” the French foreign ministry said on Monday, as an Iraqi court sentenced a fourth French citizen to death, a day after handing capital punishment sentences to three others.

The foreign ministry said the detained men were receiving consular assistance to ensure they had legal representation ahead of an expected appeal, which they have 30 days to lodge. It added, however, that France “respects the sovereignty of Iraq’s institutions”.

The French government has long insisted its adult citizens captured in Iraq or Syria should face trial locally, refusing to repatriate them despite the fact they are at risk of capital punishment.

Mustapha Merzoughi, 37, was sentenced to death by hanging on Monday, according to an AFP journalist at the court. “The evidence and the confession show that you joined the Islamic State group, that you worked in its military branch,” the judge told Merzoughi before handing down his sentence.

Another French jihadist, Fodhil Tahar Aouidate, also appeared before the court on Monday, but his trial was postponed until 2 June to allow for a medical examination after he alleged he had been beaten in custody.

Aouidate, 32, made a first trip to Syria in 2013 and returned in 2014 to join Isis, according to the French judiciary. After 130 people were killed in the 2015 Paris attacks, Aouidate appeared in a video saying it was his “great pleasure and joy to see these unbelievers suffer as we suffer here”.

Their trial came a day after acourt sentenced the other three French citizens to death for joining Isis, making them the first French jihadists to be handed capital punishment sentences. Captured in Syria by the Syrian Defence Forces (SDF), Kevin Gonot, Leonard Lopez and Salim Machou were transferred to Iraq for trial.

Iraq has taken custody of thousands of jihadists, and the Iraqi judiciary said recently it had tried and sentenced more than 500 suspected foreign Isis members since the start of 2018. Its courts have condemned many to life in prison and others to death, though none have yet been executed.