In an impassioned audio address, the leader of Islamic militant group ISIS has declared that Muslims will continue fighting until they conquer Rome.

Abu Bakr al-Baghdadi used his latest message to call his radical followers to "rush" to his newfound pan-Islamic state, a stretch of land across Iraq and Syria where he has instated himself as leader, or 'Caliph'.

"Rush O Muslims to your state. Yes, it is your state. Rush, because Syria is not for the Syrians, and Iraq is not for the Iraqis. The land is for the Muslims, all Muslims," he urged.

"This is my advice to you. If you hold to it you will conquer Rome and own the world, if Allah wills.

"O Muslims everywhere, whoever is capable of performing hijrah to the Islamic State, then let him do so, because hijrah to the land of Islam is obligatory...immigration to the house of Islam is a duty," he insisted.

Baghdadi also rallied his fellow extremists to continue fighting for their cause – urging them "to arms, to arms, soldiers of the Islamics, fight, fight".

"In this virtuous month [Ramadan] or in any other month, there is no deed better than jihad in the path of Allah, so take advantage of this opportunity and walk in the path of your righteous predecessors," he continued.

Himself holding a PhD in Islamic studies, Baghdadi urged "judges and those who have military and managerial and service skills, and doctors and engineers in all fields" in particular to move to the Islamic State.

His call follows increasing violence across Iraq, where Sunni Muslims have captured several key northern cities.

The Telegraph reports that over 2,400 people were killed in Iraq in June, which, according to the UN, marks it as the deadliest month the country has experienced in years.

The growing violence has forced hundreds of thousands of civilians to flee Iraq, many of them Christians who face increased persecution.