Barzani offered condolence to Mustaf's family and Gorran Movement members and supporters in a message, the region’s presidency website reported.
"May his soul rest in peace," Barzani wrote in his message.
Mustafa passed away on Friday morning at the age of 73 of kidney cancer in Sulaimani.
He died only a week after nearly a nine-month stay in the UK for medical care. His wife passed away only two months ago when he could not take part in her funeral due to his health condition.
Gorran, best known as the first opposition party in the Kurdistan Region, was founded in 2009 by Mustafa, a former leader at the Patriotic Union of Kurdistan (PUK).
The party is now the second largest political force in the Kurdistan Region.
Reporter’s code: 50101
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