The comments by the militant group’s leader, Abu Bakr al-Baghdadi, came in an audio statement, his first since a US-led alliance began conducting airstrikes targeting the group in Iraq and Syria.
In the statement, released 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 follows rumours that he was killed or badly wounded in an airstrike last week.
It was not clear whether the recording was made before or after the incident.
Al-Baghdadi called for attacks in Saudi Arabia, said his caliphate was expanding across the Arab world, and called for “volcanoes of jihad” in the speech.
Baghdadi also said a US-led military campaign against his group in Syria and Iraq was failing.
There have been contradictory accounts out of Iraq following US air strikes last Friday about whether Baghdadi was wounded in a raid. The US said it could not confirm whether he was killed or wounded in Iraq following a strike near the city of Fallujah.
The speech was not dated but carried a reference to the November 7 news that US president Barack Obama had approved sending up to 1,500 more US troops to Iraq.
“Oh sons of al-Haramayn [Saudi Arabia]... the serpent’s head and the stronghold of the disease are there...draw your swords and divorce life, because there should be no security for the Saloul,” Baghdadi said, using a derogatory term to refer to the leadership of Saudi Arabia.
IS has seized swathes of Syria and Iraq, declaring a caliphate over territory it controls in June. Baghdadi said he had accepted oaths of allegiance from supporters in Libya, Egypt, Yemen, Saudi Arabia, and Algeria.
“O soldiers of the Islamic State... erupt volcanoes of jihad everywhere. Light the earth with fire against all dictators,” Baghdadi said.
Referring to US-led military action against his group, he said: “Despite this crusade campaign being the most fierce and severe of all, it is the greatest failure.
“We see America and its allies stumbling in fear, weakness, impotence and failure.”
Meanwhile US defence secretary Chuck Hagel said the US-led air war against Islamic State militants will intensify as Iraqi forces become more effective.
Hagel said: “As Iraqi forces build strength, the tempo and intensity of our coalition’s air campaign will accelerate in tandem.”
It has emerged that after seizing oil refineries to fund its self-declared caliphate, IS militants will now mint their own money.
The group plans to issue gold, silver and copper coins, according to a statement released by its beit al mal, or treasury, and posted on websites used by jihadist movements. The currency aims to replace the existing “tyrannic monetary system” that has contributed to poverty, it said.
As IS conquered territory from the Syrian city of Aleppo to Baghdad, it has sought to entrench its strict interpretation of Islam.
In issuing coins, the group is making its latest pitch for statehood, said Mohsin Khan, a senior fellow at the Atlantic Council’s Rafik Hariri Center for the Middle East. “One of the attributes of a state is that it issues its own currency,” he said. “That defines you as a state at least in the eyes of your own people and perhaps in the eyes of others.”