Earlier in the day, Castro died at the age of 90.
"Fidel Castro has died. My condolences to Cuban friends, all people of Cuba. Castro was the one of the greatest, those who had changed the world. The world will remember him," Pushkov said via Twitter.
Pushkov recalled that Castro used to be subject to pressure from the part of the United States, while his country was exposed to economic war, but Castro managed to withstand.
Fidel Castro was born in 1926 in the Cuban village of Biran. He became the country's prime minister in February 1959, and ruled Cuba as a single-party state until 2008, when his brother Raul Castro took over.
Fidel remained the first secretary of the Cuban Communist Party until April 19, 2011, when he officially announced his resignation from the post.