Ukrainian forces raised their national flag over a police station in the city of Luhansk, which was under rebel control for months, Kiev said on Sunday, in what could be a breakthrough in Ukraine's efforts to crush pro-Moscow separatists.
Even so, the Ukrainian military acknowledged Sunday that one of its fighter planes 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.
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.
Ukrainian military spokesman Oleksiy Dmitrashkovsky 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.
Donetsk, the main rebel-held city, also is suffering through fighting, including frequent shelling. Ten civilians have been killed and eight wounded in the past 24 hours, city authorities reported Sunday.
The leader of the self-proclaimed rebel government in the Donetsk region, Alexander Zakharchenko, has boasted that new military equipment was on its way from Russia. In a video posted online over the weekend, he said the shipment included tanks and some 1,200 fighters who have undergone training in Russia.
Lysenko, Ukraine’s military spokesman, said the government had information that separatists had received reinforcement from Russia, but added that there is evidence rebels are complaining about not receiving some of the equipment they have been promised.
Russia denies helping the rebels and accuses Kiev, backed by the West, of triggering a humanitarian crisis through indiscriminate use of force against Russian speakers in eastern Ukraine who reject the Ukrainian government's rule. But Ukraine's president on Friday said that Ukraine had destroyed a large number of military vehicles that had recently crossed from Russia.
Part of a large Russian aid convoy carrying supplies intended for Luhansk and other afflicted zones on Sunday headed to the section of the border closest to the city, but the 16 trucks stopped just short of the frontier crossing in the early afternoon.
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 and could be used as a guise to launch a Russian military incursion.
The Red Cross, which would have responsibility for distributing the aid, on Saturday said the main holdup was a lack of security guarantees from all sides in the conflict.
A large X-ray machine was brought to the Russian crossing point in the afternoon, and Paul Picard, the head of a border-monitoring mission from the Organization for Security and Cooperation in Europe, said it would be used to inspect the cargo.
As the status of the Russian aid convoy remained uncertain, the foreign ministers of Ukraine, Russia, Germany and France were expected to meet in Berlin on Sunday evening over the crisis.