YEREVAN, Armenia — The spokesman for the president of the separatist government in Nagorno-Karabakh on Monday confirmed that Azerbaijani forces have taken control of a strategically key city and said they were nearing the region’s capital.

The statement on Facebook by Vagram Pogosian came a day after Azerbaijani President Ilham Aliyev claimed his country’s soldiers had taken Shushi.

The seizure is the most significant military development in the fighting over the territory, which is within Azerbaijan but has been under the control of ethnic Armenian forces backed by Armenia since 1994.

Shushi’s position above the regional capital Stepanakert, which is about 10 kilometers (six miles) to the north, gives strategic advantage to whomever holds it. The city also lies along the main road connecting Stepanakert with Armenia.

Long lines of vehicles have jammed the road as Nagorno-Karabakh residents flee the fighting into Armenia.