Islamic State: 'Baghdadi message' issued by jihadists
Islamic State has released an audiotape it says was recorded by its leader, Abu Bakr al-Baghdadi, days after reports that he had been killed or injured.
In the recording, released via social media, the speaker says IS fighters will never stop fighting "even if only one soldier remains".
Correspondents say the recording appears authentic and recent.
BBC analysts say the message is probably also intended to counter the claim that Baghdadi has been killed.
The IS leader was said to have been caught in a US-led air strike near the Iraqi city of Mosul last week.
Thursday's 17-minute recording makes no direct reference to that air strike, but does mention some developments that have occurred since then.
An English transcript of the recording was also released.
Meanwhile, US Defence Secretary Chuck Hagel said the US-led coalition fighting IS was making progress, but must "prepare for a long and difficult struggle".
The IS audiotape mentions US President Barack's Obama decision to deploy an extra 1,500 troops to Iraq - a move announced shortly after the air strike on Mosul.
BBC Arab affairs editor Sebastian Usher says the tone of the recording is characteristically defiant and incendiary, and the cadences and language do sound like those of the Islamic State leader.
The recording calls on IS supporters to "erupt volcanoes of jihad" across the world.
He disparages opponents of IS as "Jews, Crusaders, apostates... [and] devils", and says the US and its allies "are terrified, weak and powerless".
The recording also calls for attacks in Saudi Arabia - describing Saudi leaders as "the head of the snake" - and says that the US-led military campaign in Syria and Iraq is failing.
Gulf state rulers, who have joined the US-led coalition against IS, are described as "treacherous".
Analysis: BBC Security Correspondent Frank Gardner
All week rumours have swirled around the status of Islamic State's elusive leader. Within hours of new, unsubstantiated claims on Thursday that he had died, an audio message emerged purporting to be from him, promising an expansion of IS's campaign into new countries. It calls for attacks on the "'Land of the Two Holy Mosques", meaning Saudi Arabia, listing Shia Muslims as the top target.
It mentions new oaths of allegiance from jihadists in Egypt, Algeria and Libya and mocks the announcement of 1,500 additional US military advisers in Iraq, saying US-led air strikes had failed to stop the advance of Islamic State.
In fact the airstrikes have done exactly that in military terms, driving IS fighters off key dams, but there is no denying the spread of IS's popularity among violent extremists across the Middle East and even in Europe.
The recording also refers to new pledges of allegiance from jihadist groups in Libya, Egypt and Yemen that occurred in recent days.
"O soldiers of the Islamic State... erupt volcanoes of jihad everywhere. Light the earth with fire against all dictators," the voice on the recording says.
In Washington on Thursday, US Defence Secretary Chuck Hagel told Congress that there had been "steady and sustainable progress" against IS.
In contrast to the audio messaging disparaging the coalition efforts, Mr Hagel said US-led air strikes had helped in "degrading and destroying Isil's [IS] war fighting capacity and in denying safe haven to its fighters".
"Directly and through support of Iraqi forces, coalition air strikes have hit Isil's command and control, its leadership, its revenue sources... and impaired its ability to amass forces," he added.
The self-styled Islamic State - a jihadist group also known as Isis, or Isil - has seized swathes of Syria and Iraq since June, declaring a caliphate over territory it controls.
It emerged on Thursday that the group has reportedly announced plans to mint its own gold, silver and copper coins.
A statement posted on jihadist sites, which could not be independently verified, said the coins were to be used in IS-controlled areas.
The statement said this would counter "the tyrannical currency system that was imposed on the Muslims" - thought to be a reference to the US dollar.
Abu Bakr al-Baghdadi himself is a shadowy figure who only showed himself publicly for the first time in a video released in July, when he delivered a sermon in Mosul, Iraq.
He claims lineage from the family and tribe of the Prophet Muhammad.
Although currently limited to Iraq and Syria, IS has promised to "break the borders" of Jordan and Lebanon and to "free Palestine".
The group has attracted support from extremists around the world and demands that all swear allegiance to its leader.
Its brutal tactics - including mass killings and the beheadings of soldiers and journalists - have sparked fear and outrage across the world, including from Muslim groups.
In February, al-Qaeda disavowed IS for its actions in Syria.