AL-DHAFRA, United Arab Emirates (AFP) - France has joined Britain in carrying out reconnaissance flights in support of the United States air campaign against jihadists launched in Iraq early last month, the defence minister said on Monday.

"This very morning, the first reconnaissance flights will be carried out in agreement with the Iraqi and Emirati authorities," Defence Minister Jean-Yves Le Drian told French troops, including pilots, at the Al-Dhafra base in the United Arab Emirates.

Shortly afterwards, two French Rafale fighter jets took off from the base, an AFP correspondent reported.

Le Drian's visit came as Paris prepared to host an international conference on a fightback against militants of the Islamic State of Iraq and Syria (ISIS), who have seized swathes of Iraq and neighbouring Syria. The conference has been given added urgency by the beheading of a third Western hostage, British aid worker David Haines, on Saturday.

Britain had already been conducting extensive surveillance flights over Iraq in support of the US from its regional base in Cyprus, but has so far held back from carrying out strikes on ISIS targets.

Mr Le Drian said his trip to the base "comes at a time of extreme seriousness" over the threat posed by ISIS.

"We must be ready to intervene," he told the French troops at the base, located about 30km south-west of UAE capital Abu Dhabi.

"France stands ready at a time that is decisive for its security - because it is also France's security that is threatened by this... pseudo-Islamic State," Mr Le Drian said.

Mr Le Drian was to meet Abu Dhabi Crown Prince Mohammed bin Zayed al-Nahayan later, before heading to Egypt.