An ideological spring cleaning of sorts is set to begin in Ukraine, after President Petro Poroshenko signed controversial legislation on Friday intended to rid the country of symbols from its Soviet past.

The legislation, passed by Parliament on April 9, condemns the communist authorities that governed from 1917 to 1991 as a criminal regime. It also bans all communist symbols and propaganda, which means thousands of monuments to Bolshevik Revolution leader Vladimir Lenin and other Soviet-era icons scattered around Ukraine must be demolished.

Poroshenko's spokesman, Svyatoslav Tsegolko, called the move a "giant step forward for Ukraine."

Україно, ще один гігантський крок в майбутнє зроблено. Президент підписав закони про декомунізацію. — Svyatoslav Tsegolko (@STsegolko) May 15, 2015

Under the new laws, what Russians call the Great Patriotic War will now officially be known as the Second World War from 1939 to 1945, and state archives from the Soviet period, including those of its shady security services, are to be made public.

Perhaps the most controversial part of the legislation gives state recognition to the Ukrainian Insurgent Army, or UPA, an underground militia group created in 1942 that fought both the German and Soviet armies during World War II. Some of its members are believed to have collaborated with the Nazis in murdering thousands of Poles and Jews in western Ukraine.

Violators of the laws — who, for example, promote the hammer and sickle or publish material in print or in the media that denies the criminal nature of the Soviet regime — face up to five years' imprisonment.

The legislation applies the same treatment to the Nazi government, which invaded and controlled much of Ukraine during the war.

Ukrainian President Petro Poroshenko laid flowers at a monument to World War II victims during the anniversary of the victory over Nazi Germany, in Ukraine's capital Kiev on May 9.

The laws have drawn heavy criticism from Russia, whose state-run media have pointed to other controversial laws passed by Ukraine's fledgling post-revolution government to show what they say are attempts by Kiev to exterminate the country's Russian and Russian-speaking population.

The bills have detractors in Ukraine, too.

Halya Coynash of the Kharkiv Human Rights Protection Group said Saturday that the "divisive and flawed" legislation "effectively criminalizes public expression of views held by many Ukrainians." She also warned last month that a populist move at a time when "unity is paramount" in Ukraine "will be used in propaganda against Ukraine, with some of that propaganda, unfortunately, being difficult to refute."

Ukrainians celebrate the 70th anniversary of the victory over the Nazis at a war memorial in Kiev on May 9.

The bills were also seen as controversial by 69 Western historians from Canada, the United States and Europe. They penned an open letter to Poroshenko urging him to veto it, a move that proved futile.

Ukrainians and Ukraine-watchers on Twitter voiced their concern, too.

The decommunization law signed by Poroshenko makes Ukraine a more Soviet, taboo-ridden country than it was before. A sovok victory. — Leonid Ragozin (@leonidragozin) May 16, 2015

I am NOT a fan of communism.But this is just wrong!President signs dangerously flawed ‘decommunization’ laws #Ukraine http://t.co/HOi4sZ6ejZ — Maria Y (@Maria_DY) May 16, 2015

The legislation is certain to inflame tensions between Kiev and Moscow over Russia's annexation of Crimea last year and its support for separatists in eastern Ukraine at a time when the conflict there is just one act away from a return to all-out war.

More than 6,100 people have been killed since fighting erupted 13 months ago.