ISIS Iraq Syria
Members loyal to the Islamic State in Iraq and the Levant (Isis) wave Isis flags as they drive around Raqqa.Reuters

A top Jordanian jihadi ideologist has criticised the Islamic State of Iraq and the Levant's (Isis's) declaration of a caliphate in Iraq and Syria, suggesting it has potential to cause reprisals against Muslims around the world.

"Can every Muslim and weak person find refuge in this caliphate? Or would it be like a sharp sword against all opponents?" asked Issam Barqawi, otherwise known as Abu Mohammad al-Maqdessi.

"What would the fate be of other Islamist fighters in Iraq, Syria and elsewhere?" he continued.

Maqdessi was freed from prison on 16 June after being jailed for recruiting fighters for the Taliban and was once a mentor to al-Qaeda's Iraqi leader Abu Musab al-Zarqawi.

Writing on Facebook and on jihadist websites, he warned of "Muslims who kill other Muslims," adding: "Do not think you can silence the voice of justice by shouting, making threats, aggression and having no manners?

"Reform yourselves, repent and stop killing Muslims and distorting religion."

The terror group last week declared the caliphate, which extends from Aleppo in northern Syria to Diyala province in eastern Iraq, with Abu Bakr al-Baghdadi being named the Caliph and "leader of Muslims everywhere."

In his first statement since Isis renamed itself the Islamic State and declared the caliphate, Baghdadi told Muslims around the world to take up arms and join his extremist group.

"So take up arms, take up arms, O soldiers of the Islamic State! And fight, fight," he said in a Ramadan message.

As the group continues to gain ground in both Iraq and Syria, Saudi Arabia's King Abdullah has ordered "all necessary measures" to be implemented while Israel is to build a security fence along the Jordanian border to counter the jihadi threat.