"Some Cubans living in Russia and Cuba have become part of the military units fighting in Ukraine," the ministry said in a statement.
The Cuban government, which is a close ally of Russia, emphasized in its statement that they are not a party to the war. However, there was no response from Russia to this statement.
The Cuban Foreign Ministry did not answer questions about who was behind the gang.
Russian President Vladimir Putin ordered an increase in the number of troops in Ukraine in August after heavy losses in the conflict. According to the Russian newspaper Ryazan Gazette, following this order, some Cubans living in Russia joined the troops fighting in Ukraine in exchange for the promise of Russian citizenship.
Images purporting to show a group of Serbian citizens training to fight alongside Russian troops in Ukraine were also previously shared.
"Cuba has historically been firmly opposed to the use of mercenaries. We will continue our resolute fight against human traffickers who operate to recruit Cuban citizens in any country," The Cuban Foreign Ministry said in a statement.
This was an unusual statement for Cuba, which has recently strengthened trade ties with Russia.
The defense ministers of Cuba and Russia met in Moscow two months ago and Russian Foreign Minister Sergey Lavrov visited Cuba in April. Following the Cuban Revolution in 1959, the country became a close ally of the Soviet Union. Close relations continued after the collapse of the Soviet Union.