WASHINGTON (Reuters) - The U.S. military confirmed on Friday that a British hacker who was one of the Islamic State movement's top computer experts and active in encouraging people abroad to carry out "lone wolf" attacks was killed in Syria by a U.S. air strike.

Junaid Hussain of Birmingham, England, was killed on Aug. 24 by a U.S. military air strike on the Islamic State stronghold of Raqqah, said Air Force Colonel Pat Ryder, a spokesman for U.S. Central Command.

Hussain had been involved in "actively recruiting ISIL sympathizers in the west to carry out 'lone wolf' style attacks," Ryder said, using an acronym for the militant group that has seized large parts of Syria and Iraq.

Hussain was responsible for releasing personal information of around 1,300 U.S. military and government employees in recent weeks, and "sought to encourage" attacks against them, U.S. officials said.

One official, speaking on condition of anonymity, said Hussain had also been linked to the release of the names, addresses and photos of 100 U.S. service members on an Islamic State website in March.

Another official said that Washington had evidence that Hussain was in contact with two men who were shot dead when they tried to attack a "Draw Mohammed" cartoon contest in Garland, Texas in early May.

Islamic State claimed in a radio message after the shooting that the two men were "brothers" connected to the group.

The attack on Hussain was the second killing of a senior Islamic State figure by U.S. forces in the last 10 days. Islamic State's second-in-command was killed in a U.S. air strike near Mosul, Iraq, on Aug. 18.

The strike that killed Hussain was among the first directed specifically at an individual involved mainly in Islamic State’s extensive cyber and social media campaigns.

But U.S. and European officials stressed that Hussain had also played a larger operational role within ISIL, helping target attacks, recruiting and logistics.

"This individual was very dangerous. He had significant technical skills, and he had expressed a strong desire to kill Americans, and recruit others to kill Americans," Ryder said.

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U.S. officials said Islamic State's efforts at hacking into computer systems have largely been quite primitive.

But its use of social media to promote its cause and recruit and inspire foreign fighters to join IS in Syria or carry out attacks in their own countries has been effective.

Hussain left Britain to join Islamic State some time in the last two years. He was jailed in Britain in 2012 for hacking former Prime Minister Tony Blair's address book from an account maintained by a Blair adviser.

(Reporting by Mark Hosenball and Andrea Shalal in Washington; Editing by David Storey and Alan Crosby)