Washington called Monday for the battle against the Islamic State group to be extended to the Internet, as coalition partners met for talks on how to stop the jihadists' online propaganda.

Opening the talks in Kuwait City, retired US general John Allen said IS was promoting its "horrendous brand of warfare" online, where it "recruits and perverts the innocent".

"It is only when we contest ISIL's presence online, deny the legitimacy of the message it sends to vulnerable young people... it is only then that ISIL will truly be defeated," Allen said, using an alternative name for the extremist group.

Allen, who is coordinating the US-led campaign against IS, was meeting with representatives of coalition countries including Bahrain, Britain, Egypt, France, Iraq, Jordan, Lebanon, Oman, Qatar, Saudi Arabia and the United Arab Emirates.

IS, which has seized large parts of Syria and Iraq and declared an Islamic "caliphate", operates a sophisticated online presence, posting frequent propaganda videos and publishing its own expertly designed magazine.

Some of the videos have featured brutal atrocities, including the on-camera beheadings of two US journalists and two British aid workers.

IS and its supporters also have a strong presence on social media, which has become an important recruitment tool to attract foreign fighters to their cause.

Western governments have been increasingly alarmed by the numbers of Europeans and Americans making their way to Syria to fight with IS.

Concern is also growing over the group's online influence among disaffected young Muslims living in the West and its calls for them to carry out attacks on Western targets.

Allen said the talks in Kuwait would focus on "how to degrade and defeat ISIL's messaging and how we can all confront and contest its presence in the information space and online."

This would require a "holistic, coordinated approach at the international, regional and local levels, combining military, law enforcement, intelligence, economic and diplomatic tools."

Washington has built up a coalition of Western and Arab nations to combat IS, launching a series of air strikes against it in Iraq and Syria and backing local ground forces including the Iraqi army, Syrian rebels and Kurdish militia forces.