An Assyrian group says Islamic State militants have released 25 more Assyrian Christian hostages they had held captive in Syria for 10 months.

The 25 Christians were part of about 230 Assyrian Christians that were captured by the extremist group after it overran Assyrian communities on the southern bank of the Khabur River in the northeastern Syrian province of Hassakeh.

The Stockholm-based Assyrian Human Rights Network said the 25 arrived in the Christian town of Tal Tamr on Friday. It said the released included 16 children and their mothers.

It says the release brings the number of Assyrian hostages that have so far been released to 148.

Osama Edward, the network's director, said the release was the result of mediators who negotiated between the church and IS.