The Russian invasion is set to last for around four more months, Ukraine's ministry of defence claims.
Vladimir Putin 's "special military operation" is likely to end in September, according to alleged information said to have been leaked from within his own army.
A statement from the ministry's main intelligence directorate, released on Tuesday, also said the "occupiers" of port city Mariupol today are carrying out "big cleaning" in which they are burning dead bodies in three mobile crematoria.
These "occupiers" are considering formerly annexing it and other captured territories in the south, alongside occupied Crimea for "further integration into the Russian economic space".
This is part of a larger "corresponding plan" with a deadline of at least 2030, announced by the so-called "head" of Crimea on information policy, Oleg Kryuchkov on Sunday (May 1).
As part of the integration of Mariupol, the Russian Government has ordered seals and stamps for "occupation administration" with the inscription: " Russia, the Republic of Donbas, Mariupol, the military-civil administration".
The MOD adds, such "new 'attributes'" will be given to a list of institutions, including education, hospitals, police, registry offices and administration.
But points out: "Even though most of them are now completely destroyed by Russian troops."
The city has seen some of the most sustained bombing and missile attacks of any during the invasion, with a previously estimated 90% of it left in ruins.
Similar stamps and seals are also set to be ordered for occupied Kherson for next month.
Port city Henichesk, which lies in the Kherson oblast, is said to have seen an attempt by newly appointed 'head of the city council' Andriy Klochko raising a "solemn" Russian flag on Sunday.
This is understood to have been part of the occupation regime's plan to get the local population on board but "townspeople ignored the racist 'holiday'", the MOD added.
The statement concludes: "Among the military of the occupier's army there is information that the term of the so-called 'special military operation' is set for September 2022."
It comes after the General Staff of the Armed Forces of Ukraine announced in mid March that Russia was conducting propaganda work in the Armed Forces of the Russian Federation regarding the need to end the war by May 9.
On that date, it is expected invaders will host a Victory Day parade in Mariupol.
Victory Day is celebrated in Russia to commemorate the triumph of the allied forces over Nazi Germany in 1945.
Putin has used it to promote himself and Russia.
