LONDON (Reuters) -Britain's government on Saturday described mixed progress for Ukrainian and Russian forces fighting in southern and eastern Ukraine over the past 48 hours.
"In some areas, Ukrainian forces have likely made good progress and penetrated the first line of Russian defences. In others, Ukrainian progress has been slower," Britain's Ministry of Defence said in a statement.
Kyiv said there had been heavy fighting in the eastern region of Donetsk on Friday, and a military spokesperson said Ukrainian forces had gained more ground near the devastated city of Bakhmut.
Russia says Ukraine's counteroffensive has failed so far. Ukraine has not said the counteroffensive has actually begun - nor is it likely to - although the consensus among military analysts seems to be that it has.
With virtually no independent reporting from the front lines and Kyiv saying little, it was impossible to assess whether Ukraine was penetrating Russian defences in its bid to drive out occupying forces.
"Russian performance has been mixed," the statement from the British government said on Saturday.
"Some units are likely conducting credible manoeuvre defence operations while others have pulled back in some disorder, amid increased reports of Russian casualties as they withdraw through their own minefields."
The counteroffensive is ultimately expected to involve thousands of Ukrainian troops trained and equipped by the West. The United States announced an extra $2.1 billion in security assistance on Friday, including air defence and ammunition.
Russia, which has had months to prepare its defensive lines, says it has repelled attacks since the start of the week. Kyiv has said its main effort has yet to begin.
(Reporting by Andy Bruce; Editing by Alex Richardson and Hugh Lawson)