Ukraine says troops entered rebel-held city

Army troops have penetrated deep inside a rebel-controlled city in eastern Ukraine in what could prove a breakthrough development in the four-month-long conflict, the Ukrainian government said Sunday.

However, the military acknowledged that a fighter plane was shot down by the separatists, who have been bullish about their ability to continue the battle and have bragged about receiving support from Russia. A column of several dozen heavy vehicles, including tanks and at least one rocket launcher, was spotted rolling through rebel-held territory on Sunday.

Ukraine’s national security council said government forces captured a district police station in Luhansk on Saturday after bitter clashes in the Velika Vergunka neighborhood.

Weeks of fighting have taken their toll on Luhansk, which city authorities say has reached the verge of a humanitarian catastrophe. The siege mounted by government forces has ground delivery of basic provisions to a halt and cut off power and running water.

Although rebel forces have regularly yielded territory in recent weeks, they have continued to show formidable fighting capabilities.

Oleksiy Dmitrashkovsky, a Ukrainian military spokesman, said Sunday that the separatists shot down a Ukrainian fighter plane over the Luhansk region after it launched an attack on rebels. The pilot ejected and was taken to a secure place, he said. Another military spokesman, Andriy Lysenko, later said that the status of the pilot was still being clarified.

The column of armored vehicles spotted southeast of Luhansk was heading west, deeper into rebel-held territory. It was unclear whether the column had come from Russia.

The area is just across the border from where a large Russian aid convoy is poised to cross with supplies intended for Luhansk and other afflicted zones.

Part of the aid convoy headed to the frontier crossing Sunday, but the 16 white trucks then stopped. The convoy of nearly 270 vehicles has been marooned for days in a town near the border amid objections from Ukraine, which initially complained that the mission was not authorized by the International Committee for the Red Cross.

The Red Cross said Saturday that the main holdup was a lack of security guarantees from all sides in the conflict.

As the status of the Russian aid convoy remained uncertain, the foreign ministers of Ukraine, Russia, Germany and France met in Berlin on Sunday to discuss ways to end the crisis.

Fighting, including frequent shelling, is also affecting Donetsk, Ukraine’s main rebel-held city. Ten civilians have been killed and eight wounded in the past 24 hours, city authorities reported Sunday.