The British government on Saturday described mixed progress by Ukrainian and Russian forces fighting in southern and eastern Ukraine over the past 48 hours.

“In some areas, the Ukrainian forces have probably made good progress and have penetrated the first line of the Russian defenses. In others, Ukrainian progress has been slower,” the British Defense Ministry said in a statement.

Kyiv confirmed heavy fighting in the eastern Donetsk region on Friday, and a military spokesman said Ukrainian forces had gained more ground near the devastated city of Bakhmut.

For its part, Russia assured that Ukraine’s counteroffensive had so far failed. Ukraine has not said that the counteroffensive has actually started, nor is it likely that it will, although the consensus among military analysts seems to be that it has.

With virtually no independent reports from the front lines and Kyiv saying little, it was impossible to assess whether Ukraine was penetrating Russian defenses in its attempt to drive out the occupying forces.

“Russia’s performance has been mixed,” the British government statement said on Saturday.

“Some units are likely conducting credible maneuver defense operations, while others have withdrawn in disarray, amid rising reports of Russian casualties as they withdraw through their own minefields.”

Ultimately, the counteroffensive is expected to involve thousands of Western-trained and equipped Ukrainian troops. The United States on Friday announced an additional $2.1 billion in security assistance, including air defense and munitions.

Russia, which has had months to prepare its defensive lines, says it has repelled all attacks since the start of the week. Kyiv has said that its main effort has not yet started.