Russian forces appear poised to intensify their offensive to capture the whole of the eastern Ukrainian regions of Donetsk and Luhansk as more Ukrainian fighters surrender at a steel plant in Mariupol. But Ukrainian forces may be preparing to mount counterattacks on all fronts.

The Russian defense ministry said on Thursday that its missile attacks destroyed artillery weapons, ammunition depots and anti-aircraft missile systems in Donetsk and the southern region of Mykolaiv.

The ministry added that a total of 1,730 fighters had surrendered at the Azovstal steel plant in Mariupol since Monday. Russian forces are likely to take full control of the strategic city in the near future.

Meanwhile, the British defense ministry said on Thursday that, "In recent weeks, Russia has fired senior commanders who are considered to have performed poorly during the opening stages of its invasion of Ukraine."

The ministry said that "Lieutenant General Serhiy Kisel, who commanded the elite 1st Guards Tank Army, has been suspended for his failure to capture Kharkiv" in eastern Ukraine.

The ministry also said that "Vice Admiral Igor Osipov, who commanded Russia's Black Sea Fleet, has also likely been suspended following the sinking of the cruiser Moskva in April."

The ministry pointed out that "many officers involved in the invasion of Ukraine will likely be increasingly distracted by efforts to avoid personal culpability for Russia's operational setbacks."

It said that "this will likely place further strain on Russia's centralised model of command and control, as officers increasingly seek to defer key decisions to their superiors."

The ministry determined that "it will be difficult for Russia to regain the initiative under these conditions."

Ukrainian forces are putting up all-out resistance. An adviser to Ukraine's internal affairs minister stressed that Russia will feel a counterattack quite seriously in late June or early July.

In an interview made public on Tuesday, Ukrainian Foreign Minister Dmytro Kuleba indicated that a victory over Russia needs to include liberating all the Donbas region and Crimea. The Donbas refers to Donetsk and Luhansk in eastern Ukraine. Crimea was unilaterally annexed by Russia in 2014.