Evgeniy Maloletka, Associated Press
Ukrainian government soldiers sit atop of a tank with the words reading "To Lviv" in Donetsk region, eastern Ukraine, Saturday, Aug. 9, 2014. A top commander of the pro-Russia insurgency in eastern Ukraine said Saturday that Ukrainian forces have seized Krasnyi Luch a key town, leaving the rebel region's largest city of Donetsk surrounded. Lviv is an Ukrainian town.

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.

Russia has been pushing for a humanitarian mission into Luhansk, but the Ukrainian government in Kiev and Western countries suspect that could be a pretext for sending in troops. Western countries say Russia has assembled some 20,000 troops just across the border.

The International Committee of the Red Cross said it is stepping up work to alleviate the crisis in eastern Ukraine but warned that any Red Cross aid convoy "will be taken in strict adherence to our fundamental working principles of neutrality, impartiality, and independence."

The deputy head of the Ukrainian presidential administration, Valeriy Chalyi, claimed Saturday that Russian forces wanted to enter Ukraine under the guise of a humanitarian mission but Ukraine had blocked the move.

Kremlin spokesman Dmitry Peskov denied the claim, saying "there was no attempt by Russian soldiers at penetration," according to Russian news agencies. But he reiterated Russia's call for humanitarian action, saying "this catastrophe now is the No. 1 theme for discussion."

In Kiev, city workers and volunteers on Saturday removed the last of the barricades that had blocked the capital's main street since anti-government protests began in November.

Protesters had erected the barricades to protect a sprawling tent camp on the city's main square. Although the camp's size dwindled sharply after pro-Russian President Viktor Yanukovych fled the country in February and a new government came to power, a determined core of demonstrators remained.

Some tents were still visible Saturday. But Kiev mayor Vitali Klitschko, one of the leaders of the protests against Yanukovych, was quoted by Ukrainian media as saying an agreement had been reached with the protest holdouts to restore free movement in the city.

Several Kiev protest tents caught on fire later in the day but it was not clear why.

Yanukovych's ouster precipitated the crisis in Ukraine's east, which was his support base. Fighting began in April, after Russian President Vladimir Putin annexed Ukraine's Russian-speaking Crimean Peninsula.

Peter Leonard in Kiev, Geir Moulson in Berlin and Jim Heintz in Moscow contributed to this report.