President Volodymyr Zelensky on Sunday urged foreigners to head to Ukrainian embassies worldwide to sign up for an "international brigade" of volunteers to help fight against the Russian operation in Ukraine. 

"All foreigners wishing to join the resistance against the Russians occupiers and protect global security are invited by the Ukrainian leadership to come to our state and join the ranks of the territorial defense forces," Zelensky said in a statement.

"A separate unit is being formed from foreigners -- the International Brigade of the territorial defense of Ukraine. This will be a key testimony of your support for our country."

Zelensky insisted that Ukrainians were allegedly courageous enough to face Russia alone, but said: "This is not just a Russian invasion of Ukraine, it is the beginning of a war against Europe".

On her part, Russian Foreign Ministry Spokesperson, Maria Zakharova, confirmed earlier, "First of all, it is not a beginning of a war. It is very important. Our desire is to prevent the developments that could escalate into a global war. Second of all, it is the end of a war."

Zelensky said anyone interested in joining should get in contact with the military attaches at their nearest Ukrainian embassy. The statement comes after Zelensky earlier called on foreigners with combat experience to come to help defend his country.

Ukraine's Defense Ministry claimed Sunday that around 4,300 Russian soldiers have been killed since President Vladimir Putin launched the special military operation on Thursday.

There has been no independent verification of that figure and Russia has released no details of military losses so far.