PARIS/BERLIN/BAGHDAD - A horrified France was grappling with a new reality on Thursday in which hundreds of its citizens are openly joining militant groups and directly calling for attacks on their homeland.

A new video from the Islamic State group released on militant forums and Twitter on Wednesday showed three Kalashnikov-wielding Frenchmen burning their passports and calling on Muslims to join them or stage attacks in France.

The new video explicitly calls for retaliation against France for launching air strikes against the Islamic State group, which has seized large parts of Syria and Iraq.

It follows the appearance of two other French militants - identified as 22-year-olds Maxime Hauchard and Mickael Dos Santos - in a brutal IS execution video released at the weekend.

Defence Minister Jean-Yves Le Drian announced on Wednesday that France would step up its campaign against the militants, sending six Mirage fighter jets to Jordan in December.

France currently has nine Rafale jets based in the more distant United Arab Emirates as part of a US-led international campaign to provide air support to Iraqi and Kurdish forces fighting the group.

Its most recent strikes, Le Drian said, targeted trenches used by IS fighters around the northern Iraqi city of Kirkuk on Tuesday. But France is increasingly looking inwards as it reels from the news that over 1,000 people from a wide range of backgrounds have left to join the militants in Iraq and Syria, with 375 currently there.

Meanwhile, the chief prosecutor of the International Criminal Court said she was weighing bringing war crimes charges against Islamic State militant fighters, in an interview published Thursday. Fatou Bensouda told the German daily Sueddeutsche Zeitung that such steps would be possible for extremists whose home countries have signed on to the ICC’s treaty.

“There is a lot of evidence that there are foreign fighters in the ranks of IS from countries that have signed the court’s statute, including Jordan, Tunisia and European countries,” she said. “We could prosecute these suspects for war crimes and crimes against humanity.”

Bensouda said she had already received files from the governments of Lebanon, Tunisia and Jordan and was “reviewing our options”. But she said that war was still raging in the countries where investigations were required and noted that it was increasingly difficult to fly out witnesses to testify. “More and more, we try to work with documents and not witnesses,” she said.

IS has carried out widespread atrocities since seizing control of large parts of Iraq and Syria, executing five Western hostages and hundreds of locals.

Moreover, Turkish Prime Minister Ahmet Davutoglu and his Iraqi counterpart Haidar al-Abadi held talks Thursday in Baghdad on security cooperation, in a sign of an easing in the long-strained ties between their countries. Iraq is battling to retake large areas overrun by the Islamic State (IS) militant group while Turkey borders territory which the militants control in neighbouring Syria.

Amnesty International warned Thursday that Turkey’s widely-admired response to the refugee crisis sparked by the war in neighbouring Syria is now showing its limitations, with hundreds of thousands of Syrian refugees living in destitution and others being denied entry.

Turkey has taken in 1.6 million Syrian refugees since the Syrian conflict began in 2011 but only 220,000 of these are living in refugee camps - which are now operating at full capacity - and the rest are fending for themselves, Amnesty said.

“Turkey’s response to the Syrian refugee crisis, despite its significant resource commitment and many positive policy initiatives, is increasingly showing its limitations,” it said in the report, entitled “Struggling to Survive”. “A growing number of Syrian refugees in Turkey are struggling to survive,” it said saying that hundreds of thousands were “likely to be destitute or at serious risk of destitution.”

Amnesty praised the “well-resourced” refugee camps that had been set up in Turkey and the move by the Turkish authorities to allow free healthcare to all Syrian refugees. It contrasted this with the paltry response by the international community to the crisis, complaining of “grossly insufficient funding commitments” from the West.