Russia's President Vladimir Putin will meet Belarusian President Alexander Lukashenko on Tuesday to discuss the situation in Ukraine and Western sanctions, news agencies in Russia and Belarus reported.

Russia sent tens of thousands of troops into Ukraine on Feb. 24 from both Russian and Belarusian territory in what it called a "special military operation" designed to demilitarise and "denazify" its neighbour.

Ukraine and Western governments reject that as a false pretext for an invasion, which has killed thousands and displaced millions, and has now shifted from the gates of Kyiv to the east of Ukraine where a huge offensive is expected. .

Lukashenko has insisted that Belarus must be involved in negotiations to resolve the conflict in Ukraine, saying also that Belarus had been unfairly labelled "an accomplice of the aggressor".

However, the European Union, the United States and others have included Belarus in the sweeping sanctions imposed on Russia.

Lukashenko arrived early on Tuesday in the Amur region in the Russian Far East where he is to meet Putin at the Vostochny Cosmodrome, a Russian spaceport, Belarusian Belta news agency reported.

April 12th is celebrated in Russia and some other former Soviet countries as the Cosmonautics Day, commemorating the first manned space flight made in 1961 by the Russian Soviet cosmonaut Yuri Gagarin.

(Writing by Lidia Kelly in Melbourne; Editing by Simon Cameron-Moore)