ISIL has released an audio recording it says is of its chief, Abu Bakr al-Baghdadi, days after an air strike on jihadist leaders in Iraq sparked rumours he had been wounded or killed.
In the 17-minute message, the man purported to be Baghdadi calls on supporters to "erupt volcanoes of jihad everywhere".
In particular, he calls for attacks in Saudi Arabia, telling listeners that the Gulf kingdom is the "head of the snake", and that his "caliphate" is expanding across the Arab world.
He makes no direct reference to the US air strikes against the Isil leadership last Friday, in which he was rumoured to have been killed.
However, the message includes a reference to a US announcement also made last Friday that President Barack Obama had approved sending up to 1,500 more US troops to Iraq.
The head of the extremist group says Isil "will fight to the last man", and will "continue to expand" despite coalition strikes.
"Despite this Crusade campaign being the most fierce and severe of all, it is the greatest failure," he says.
"We see America and its allies stumbling in fear, weakness, impotence and failure."
The comments by the militant group's leader, if verified, would be his first since a US-led alliance began conducting air strikes targeting the group in Iraq and Syria.
In the statement, released last night on social media networks, he says his fighters "will never leave fighting, even if only one soldier remains."
The recording appeared authentic, and his voice appeared to correspond with previous recordings released by the group.
Al-Baghdadi's statement came after rumours that he was wounded in an air strike. It was not clear whether the recording was made before or after the incident.
Meanwhile Syria's interim government has called on international donors to help stave off a food crisis in the country where drought and civil war have caused a dramatic drop in wheat production this year.
The UN predicted earlier this year that Syria's wheat harvest could hit a record low of between 1.7 million and 2 million tonnes, some 50pc below averages recorded between 2001 and 2011.
"While the bombardments are going on ... there is a very, very severe problem right now upcoming, and no one talks about that," Abrahim Miro, finance minister of the interim government, which is made up of opposition figures, said in Istanbul. "That problem is that we have severe food crisis coming in the coming few months."
He said there were several reasons for the shortage, but blamed it especially on very low production and the fact that much of the wheat is produced in areas held by Isil or the Syrian government of President Bashar Assad. An estimated 200,000 people have been killed in Syria since protests against Mr Assad spiralled into violence in 2011.
Mr Miro said a grain agency set up by the interim government managed to procure 18,000 tons of wheat from local farmers, but that is not enough.
He said it covers just 4pc to 10pc of the wheat required to provide bread to 2.5 million Syrians living in Aleppo, Idlib, Daraa and Quneitra provinces.
"We have a shortage of 323,000 tons," Mr Miro said. "We ask our friends to give us wheat in-kind. The ball actually is in their field. We hope they can react as soon as possible."
Also yesterday, two Syrian opposition figures claimed that Isil and al-Qa'ida's branch in the country met last week and agreed to stop fighting each other and work together against their opponents. The deal could be a heavy blow to Washington's strategy against Isil, which relies on arming moderate rebel factions to push back extremists in Syria.
A prominent Syrian opposition official and a rebel commander say delegates from the two groups met in secret on November 2. (© Daily Telegraph, London)