Kiev, June 15 : Ukraine's Deputy Defence Minister Hanna Maliar has confirmed that "extremely fierce battles" are raging in parts of the country as forces continue their counter-offensive against Russia.

Both sides were grappling with severe flooding caused by the destruction of a major dam on the Dnipro River, but east of there, the fierce combat indicated that Ukraine’s long-awaited counteroffensive against the Russian invasion was underway, according to analysts and Western and Russian officials.

Two senior U.S. officials, speaking on the condition of anonymity to discuss sensitive military operations, confirmed that Ukrainian troops had, as expected, suffered casualties and equipment losses in the early fighting, but said that classified assessments quantifying the losses were still being developed.

There was no information available on Russian losses, but attackers typically suffer heavier initial casualties than dug-in defenders, and analysts warned that breaking through the Russian lines would be difficult and come at a high price.