A Ukrainian senior defense official says Russia may step up its offensive possibly by another partial mobilization and more frequent drone attacks.

Ukraine's deputy defense minister Hanna Maliar revealed her view on social media on Wednesday.

Her comment comes while Russian forces are intensifying their offensive in the eastern region of Donetsk. The Ukrainian military said on Thursday that more than 40 settlements were attacked in and around the Ukrainian strongholds of Bakhmut and Avdiivka.

Maliar mentioned the significant human loss of Russian forces so far, adding that Moscow would likely have to announce a second partial mobilization in the first three months of this year.

She also warned that Russian forces may launch more frequent drone attacks because they have run out of precision missiles.

Russia's defense ministry says 89 Russian troops, including a local commander, were killed in a Ukrainian attack on temporary barracks on Sunday.

The ministry has blamed the strike on individual soldiers, saying the frequent use of mobile phones allowed Ukrainian forces to zero in on their positions.

But this response drew criticism even from Russian military experts who support the invasion of Ukraine. They say on social media that the defense officials' explanations are not convincing, and it is not cell phones and their users that are to blame, but the negligence of the commanders.

The Institute for the Study of War, a US think tank, said on Wednesday that such criticisms "largely converged on the incompetence of Russian military command." It pointed out that the Russian military leadership has no understanding of the basic realities on the frontline and is seeking to shift the blame for its own command failure.