Ukraine says its troops are advancing in its counteroffensive against Russian forces and has indicated a full-scale operation is still ahead.

The General Staff of the Armed Forces of Ukraine said Tuesday that its troops have partially advanced on the fronts toward Melitopol, a main city in the southern region of Zaporizhzhia, and Berdyansk, a port city facing the Sea of Azov. The officers also said the troops are entrenching themselves in the achieved positions.

Deputy defense minister Hanna Maliar said Russia is concentrating its forces in Lyman in the eastern region of Donetsk and elsewhere, making fighting fiercer. But she said the "biggest blow" is yet to come in the counteroffensive.

President Volodymyr Zelenskyy said in a video released Tuesday that Ukrainian soldiers in the east and south are "destroying the enemy," and that this will continue.

Britain's defense ministry said Wednesday, "Russia has continued to expend significant effort building defensive lines deep in rear areas, especially on the approaches to occupied Crimea." The ministry added they include a 9-kilometer-long extensive defense zone in the northern part of the peninsula.

The ministry also said, "Russia continues to see maintaining control of the peninsula as a top political priority."