Tigray rebels in Ethiopia have declared they are in a state of "full-blown war" with the federal government, raising fears of a renewed civil war in the country.

The announcement came as heavy artillery attacks were reported in neighbouring states, with Tigray rebels joining other rebel groups to seize airports and target government positions in northern Ethiopia.

Tensions between the federal government and the authorities in the northern Tigray state have been rising for months.

The two sides previously fought a devastating civil war between 2020 and 2022. According to African Union estimates, the conflict killed more than 600,000 people.

Ethiopian President Taye Atske Selassie addressed the UN General Assembly, warning of "forces of destruction and mayhem" as the situation in the north deteriorated.