February 23-26, 2015: IS kidnaps more than 220 Assyrian Christians as it seizes territory around Tal Tamr in Hasakeh province .
The fighting and kidnappings prompt around 5,000 people to flee, with many seeking refuge in the city of Qamishli which is controlled by Kurdish and regime forces and Hasakeh city, the provincial capital.
The IS reportedly releases some of the Christians after negotiations.
In early August, 2015, IS abducts 270 Christians in a central Syrian town known as a symbol of religious coexistence, Al-Qaryatain. They are kept in an underground dungeon some 90 kilometres (56 miles) away. Most are freed 25 days later and the area is retaken by regime forces in April, 2016.
January 16, 2016: 400 civilians abducted following an IS assault on the city of Deir Ezzor and taken to regions the jihadists control in the west of the province as well as to the neighbouring province of Raqa, an IS stronghold.
On January 20, 270 of the 400 are freed after being interrogated by the IS on their links with the regime.
April 4, 2016: IS abducts more than 300 workers at a cement factory outside the town of Dmeir, around 50 kilometres (30 miles) northeast of Damascus.
Four days later the group agrees to free most of the workers, and the IS-linked Amaq agency says around 300 are freed, but 20 accused of belonging to a pro-government militia are not. It says four were executed because they were Druze, an offshoot of Islam considered heretical by IS.
The Syrian Democratic Forces Arab-Kurdish alliance expelled most of the IS fighters from Manbij the previous week, but dozens continued to resist.
They withdrew from northern Manbij and headed for the IS-held town of Jarabulus along the border with Turkey, taking their captives with them.