DONETSK, Ukraine: Ukrainian forces have seized a key town and are surrounding Donetsk, the largest insurgent-held city in eastern Ukraine, a top rebel commander said Saturday.

The statement by Igor Girkin, a former Russian special services officer, appeared to be a significant admission by the rebels that Ukrainian government forces are gaining the upper hand in the four-month-old fight.

He said the town of Krasnyi Luch, which lies on one of two main roads between Donetsk and the other rebel-held city of Luhansk, “has been taken by the enemy.”

“The Donetsk-Horlivka group of the fighters of Novorossiya is completely surrounded,” he said on a rebel social media page. Novosrossiya, or “New Russia,” is a term widely used by the rebels for the eastern area that seeks independence from the government in Kiev. Horlivka, where rebels and Ukrainian forces are also fighting, is 30 kilometers (20 miles) north of Donetsk.

Seizing Krasnyi Luch would cut off many routes to other parts of the rebel-held east.

A spokesman for the Ukrainian military operation, Andriy Lysenko, told reporters Saturday that he could not confirm that the town was under government control.

In Donetsk, a city spokesman said at least one person was killed and several injured Saturday in shelling of the city’s southern area. Spokesman Maxim Rovninsky also told The Associated Press that about 30 apartment blocks came under fire during the night.

The city, whose population was nearly 1 million before the fighting but has seen hundreds of thousands flee, has increasingly come under fire over the past weeks. Ukrainian officials deny that they are shelling civilians, as rebels claim, and say the rebels are putting rocket launchers in populated areas.

Explosions were also heard Saturday on the northern outskirts near Donetsk’s airport.

Concerns are rising about a looming humanitarian catastrophe in Luhansk, where fighting has been heavier and more prolonged. A map released by the Ukrainian military shows Ukrainian forces near the outskirts of Luhansk on three sides, with an opening to other rebel-held territory only at the south.

Russian news agencies quoted Luhansk authorities as saying Saturday that the city has been without water and electricity for a week and most of its stores are closed.