Belarusian President Alexander Lukashenko said he was forming a southern military command and sending battalion tactical groups to the area that borders Ukraine.
Lukashenko did not give details, but battalion tactical groups typically consist of mechanized infantry including tanks. The territory of Belarus was used for rocket attacks on Ukraine, but the military of Belarus did not take part in the Russian ground operation.
Ukrainian authorities have expressed concern that Belarus may agree to a wider participation in the war.
Western allies are considering whether to allow Russian oligarchs to buy their way out of sanctions and using the money to rebuild Ukraine, according to government officials familiar with the matter.
Canadian Deputy Prime Minister and Finance Minister Chrystia Freeland proposed the idea at a G-7 finance ministers' meeting in Germany last week.
Freeland raised the issue after oligarchs spoke to her about it, one official said. The Canadian minister knows some Russian oligarchs from her time as a journalist in Moscow. The official said the Ukrainians were aware of the discussions. The official said it's also in the West's interests to have prominent oligarchs dissociate themselves with Russian President Vladimir Putin while at the same time providing funding for Ukraine.
The officials spoke on condition of anonymity as they were not authorized to speak publicly about internal G-7 discussions.
Finland's Prime Minister Sanna Marin has become the latest European leader to visit Ukraine.
Marin met with Ukrainian President Volodymyr Zelenskyy on Thursday in Kyiv.
Finnish public broadcaster YLE says she also visited the towns of Bucha and Irpin where Russian soldiers are alleged to have killed civilians.
Zelenskyy thanked Marin for Finland's weapons deliveries and its support for sanctions against Russia.
Jolted by Russia's invasion of Ukraine, Finland recently broke with its policy of non-alignment and applied for membership in NATO, together with neighboring Sweden.
The head of the Russia-backed separatist region in eastern Ukraine says that there may be more Ukrainian fighters hiding at the sprawling Azovstal steel mill in Mariupol, even after Moscow officially declared the operation of taking control over it successful and completed.
Denis Pushilin of the Donetsk People's Republic said of the Ukrainian fighters on Thursday: "They could be hiding....They could be lost somewhere, lagged behind" the ones who surrendered and were captured.
The Russian military declared Azovstal and all of Mariupol "completely liberated" on May 20 and reported that a total of 2,439 fighters had come out of the last pocket of Ukrainian resistance in the besieged city.