Paris, Sep 15 (IANS): Senior leaders from a US-led coalition formed to combat the Islamic State (IS) terrorist organisation Monday gathered in Paris to discuss how to defeat the group that has seized large swathes of territories in Iraq and Syria since June.

French President Francois Hollande said there was "no time to lose" in confronting the jihadi threat, France 24 reported.

Ten Arab states - including Saudi Arabia - are among the countries backing the coalition.

Representatives of 20 nations are taking part in the summit, including US Secretary of State John Kerry, Iraqi President Fuad Masum and Russian Foreign Minister Sergei Lavrov, for talks focused on defining the specific role each nation would play in the fight against the militant group.

The meeting is being held after the Islamist group beheaded British aid worker, David Haines, Saturday, the third grisly beheading of a Westerner in recent weeks.

British Prime Minister David Cameron Sunday vowed that Britain would hunt down those responsible for the gruesome killing of Haines, 44, describing the jihadis as the "embodiment of evil".

The IS, previously known as the Islamic State of Iraq and Greater Syria (ISIS), has issued a death threat against another British captive, Alan Henning.