According to the Ministry of Foreign Affairs of Ukraine, from March 1, 2020, Ukrainian citizens need a foreign passport to travel to the Russian Federation.
A civil passport and a birth certificate for children under the age of 16 will no longer be used to leave Ukraine.
Ukrainian citizens who return home from Russian Federation are able to enter Ukraine with their civil passports and birth certificates though.
This decision was made by Ukrainian government in order to prevent the use of fake documents and the illegal removal of children.