"The countries here mentioned have decided on the formation of a military alliance led by Saudi Arabia to fight terrorism, with a joint operations centre based in Riyadh to coordinate and support military operations," the statement said.

A long list of Arab countries such as Egypt, Qatar, the United Arab Emirates, together with Islamic countries Turkey, Malaysia, Pakistan and Gulf Arab and African states were mentioned.

The announcement cited "a duty to protect the Islamic nation from the evils of all terrorist groups and organizations whatever their sect and name which wreak death and corruption on earth and aim to terrorize the innocent."

Shi'ite Muslim Iran, Sunni Saudi Arabia's arch rival for influence in the Arab world, was absent from the states named as participants, as proxy conflicts between the two regional powers rage from Syria to Yemen.

The United States has been increasingly outspoken about its view that Gulf Arab states should do more to aid the military campaign against the Islamic State militant group based in Iraq and Syria.

In a rare press conference, 30-year-old crown prince and Defence Minister Mohammed bin Salman told reporters on Tuesday that the campaign would "coordinate" efforts to fight terrorism in Iraq, Syria, Libya, Egypt and Afghanistan, but offered few concrete indications of how military efforts might proceed.

"There will be international coordination with major powers and international organisations ... in terms of operations in Syria and Iraq. We can't undertake these operations without coordinating with legitimacy in this place and the international community," bin Salman said without elaborating.

Asked if the new alliance would focus just on Islamic State, bin Salman said it would confront not only that group but "any terrorist organisation that appears in front of us."

Saudi Arabia and its Gulf Arab neighbours have been locked in nine months of warfare with Iran-allied rebels in neighbouring Yemen, launching hundreds of air strikes there.

Especially after a rash of attacks on Western targets claimed by Islamic State in recent months, the United States has increasingly said it thinks that firepower would better be used against IS.

As a ceasefire is set to take hold in Yemen on Tuesday alongside United Nations-backed peace talks, Riyadh's announcement may signal a desire to shift its attention back toward the conflicts north of its borders.

Islamic State has pledged to overthrow the monarchies of the Gulf and have mounted a series of attacks on Shi'ite Muslim mosques and security forces in Kuwait and Saudi Arabia.