RUSSIA is pouring reinforcements into eastern Ukraine ahead of a new offensive that could begin next week along a front where there have been relentless battles for months, a Ukrainian governor said.

FATE OF DEFENCE MINISTER

* Ukraine sent mixed messages about the fate of Defence Minister Oleksii Reznikov, leaving a key post in doubt. The questions over Reznikov were the first public sign of disarray in Ukraine's wartime leadership.

* Zelenskiy has fired a series of high-level officials this year in a purge aimed at clamping down on corruption. Reznikov had been under pressure over a corruption scandal in the ministry.

* Kyrylo Budanov, who has been tipped to become Ukraine's next defence minister, is a young officer who enjoyed a meteoric rise to become military intelligence chief, decorated for his role in operations that mostly remain secret.

FIGHTING IN EAST

* Serhiy Haidai, Ukraine's governor of the mainly Russian-occupied Luhansk province, said Russia was pouring in reinforcements for an offensive that could begin as soon as next week.

* Fierce battles in Ukraine's Donetsk region "are very difficult", Zelenskiy said, as Ukraine braced for a possible Russian offensive this month before the first anniversary of its invasion of Ukraine.

* Russia's defence ministry said its forces had taken control of Mykolaivka, a village in Ukraine's eastern Donetsk region, state media reported.

* Russia's state Investigative Committee said it was examining the alleged use of chemical weapons by Ukrainian forces near the eastern towns of Soledar and Bakhmut. Ukrainian forces said they had never used chemical weapons anywhere at any time.

* Reuters was not able to independently verify Russia's claim.

DIPLOMACY

* Ukrainian President Zelenskiy has been invited to take part in a summit of European Union leaders, the EU said, amid reports he could be in Brussels as soon as this week.

* U.S. Vice President Kamala Harris is expected to discuss U.S. support for Ukraine when she travels to a major European security conference in Germany next week, as Russia's invasion nears the one-year mark.

* The head of the U.N. nuclear agency, the IAEA, will visit Moscow this week, but the Kremlin said he will not meet President Vladimir Putin.

* Ukraine's main Catholic church said it would move to a new calendar that would see Christmas celebrated on Dec. 25 rather than Jan. 7, amid an effort by Ukrainian institutions to break cultural links to Russia. The decision by the Ukrainian Greek Catholic Church, which counts just less than a tenth of Ukrainians as worshippers, was welcomed by culture minister Oleksandr Tkachenko.

READ MORE: Latest development on Ukraine-Russia crisis