France has joined Britain in carrying out reconnaissance flights in support of the US 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.

Le Drian's visit to the base came as Paris prepared to host an international conference on a fightback against militants of the Islamic State, 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 IS targets