ISIS flag
ISIS flagReuters

An Egyptian court has upheld death sentences for seven people over the beheadings in Libya of 21 Christians, all but one from Egypt, and for belonging to the Islamic State (ISIS) group, a judicial official said on Sunday, according to AFP.

In February of 2015, ISIS released a video on the internet of the beheadings on a Libyan beach, sparking international condemnation and Egyptian air strikes against jihadist targets in the neighboring country.

The ruling, which was handed down on Saturday, came a day after an attack on a mosque in Egypt's Sinai Peninsula that killed more than 300 people and which ISIS is suspected of carrying out.

The court also sentenced 10 people to life in prison - 25 years in Egypt - and three others to 15 years in prison, the official said, according to AFP. The ruling can still be appealed.

The court first sentenced the seven to death in September. Three were sentenced in absentia, and an unspecified number of those sentenced were accused of having taken part in the beheadings.

Prosecutors accused the seven suspects of belonging to an ISIS cell in Marsa Matruh, northwest Egypt, and of planning attacks after having received military training at jihadist camps in Libya and Syria.

Egypt is battling a local affiliate of ISIS, calling itself the Sinai Province, which has claimed attacks that have killed more than 100 Copts since last December.

Coptic Christians make up about 10 percent of Egypt's population.