BEIRUT (Reuters) - Islamic State leader Abu Bakr al-Baghdadi called for attacks in Saudi Arabia, said his caliphate was expanding across the Arab world, and called for "volcanoes of jihad" in a speech purported to be in his name on Thursday.

Baghdadi also said a U.S.-led military campaign against his group in Syria and Iraq was failing. Reuters could not independently confirm the authenticity of the speech, which was carried on jihadist websites.

There have been contradictory accounts out of Iraq following U.S. air strikes on Friday about whether Baghdadi was wounded in a raid. The United States said on Tuesday it could not confirm whether he was killed or wounded in Iraq following a strike near the city of Falluja.

The speech was not dated but carried a reference to a Nov. 7 U.S. announcement that President Barack Obama had approved sending up to 1,500 more U.S. troops to Iraq.

"O 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.

Islamic State 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.

"Oh soldiers of the Islamic State...erupt volcanoes of jihad everywhere. Light the earth with fire against all dictators," Baghdadi said.

Referring to U.S.-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."

(Beirut bureau; Editing by Angus MacSwan)