Father Emanuel Youkhana, who leads a Christian Aid effort to help displaced believers in northern Iraq, told the Catholic News Service: "All the villages along the Khabour River have been liberated."
He also said a local clergyman in Tal Tamar village "rang the church bell to celebrate".
The militant group took more than 230 Assyrian Christians hostage from the villages in February, who are still missing according to advocacy group A Demand For Action.
Islamic State has made significant gains in Iraq and Syria recently.
Yesterday, the extremists captured the central Syrian city of Palmyra, which contains a UNESCO world heritage site.
And in the last week, militants captured the Iraqi city of Ramadi, which is 60 miles west of the capital Baghdad. Hundreds of Iraqi troops died in the conquest, before the others were forced to flee.
25,000 people were also forced to flee from Ramadi as a result, according to the United Nations.
