IS beheads US journalist
The US and British intelligence agencies have identified the black-clad executioner, who beheaded two American journalists.Screenshot of the IS video taken from SITE Intelligence

The gruesome beheading of an American photojournalist by Islamic State militants has jolted the world to the depravity of the militants and the consequences of the United States' intervention in the Iraq crisis.

Heads of several nations such as France and Britain are now seeking global action on the issue of the Islamic State, which has declared a Caliphate in the towns it captured in Iraq and Syria.

French President Francois Hollande called for an international conference to discuss a "global strategy" for combating the militants on Wednesday, after the video of the killing emerged.

"We can no longer keep to the traditional debate of intervention or non-intervention. We have to come up with a global strategy to fight this group, which is structured, has significant financing, very sophisticated weapons and threatens countries like Iraq, Syria and Lebanon," The Guardian quoted Hollande. 

British Foreign Secretary Philip Hammond said that the IS militants pose a threat to the United Kingdom and not just the Middle east, as speculations were rife that the journalist's executioner was British.

"Isis are waging a war on moderate Islamic opinion and they are waging war on the West and we have to deal with them on that basis," The Independent quoted Hammond. 

British Prime Minister David Cameron tweeted on Wednesday about the beheading and said he would call for a meeting on the situation in Iraq.

"If true, the murder of James Foley is shocking and depraved. I will today chair meetings on the situation in Iraq/Syria", he wrote. 

Iraqi Foreign Minister Hoshiyar Zebari made an appeal to the international community to support Iraq in its fight against the militants of the Islamic State, a Sunni extremeist outfit earlier known as the Islamic State of Iraq and Syria.

United States President Barack Obama is expected to make a statement on the video on Wednesday.

The issue of how the IS is financed has also prompted responses from world leaders.

German Vice Chancellor and Economy Minister Sigmar Gabriel called for a "debate" about where the militant group is getting its funds from.

US photojournalist James Foley is the first American national to become a victim of the Islamic State militants, ever since they came to prominence during the Syrian civil war in 2011.

The incident has especially highlighted the grave dangers journalists face in conflict-ridden states. According to the Committee to protect Journalists, there are about 20 journalists who are currently missing in Syria, where Foley himself had gone missing two years ago.