The European Union stands in solidarity with illegally convicted Ukrainian film director Oleh Sentsov, who has been servicing his 20-year term in a Russian penal colony, and says it expects his immediate release.

"The European Union stands in solidarity with Oleh Sentsov and, in addition to swift and appropriate medical treatment, expects his immediate release, along with all illegally detained Ukrainian citizens in Russia and on the Crimean peninsula," the EU's spokesperson said in a statement on the continued illegal detention of Sentsov, which was posted by the Mission of Ukraine to the EU on Facebook.

His health has now deteriorated to a critical state. In refusing to provide him with appropriate medical treatment in an institutionalised medical setting, the authorities of the Russian Federation have violated his human rights as well as their own human rights commitments under international law, namely the European Court of Human Rights interim measure of July 25, 2018.

Oleh Sentsov was jailed for alleged activities conducted on the Crimean Peninsula, the illegal annexation of which by the Russian Federation he strongly opposes.

"The EU considers the case to be in breach of international law and elementary standards of justice," the statement said.

"Oleh Sentsov has shown incredible courage, determination and selflessness during his 145 days of hunger strike," the spokesperson added.

Read alsoSentsov announces end of hunger strike from Oct 6 because of possible forced feeding

As UNIAN reported earlier, Sentsov was arrested in Russian-occupied Crimea in spring 2014 and in August 2015 he was sentenced to 20 years in prison following an unfair trial where he faced "terrorism" charges stemming from his opposition to Russia's occupation of Crimea.

He has been serving his term in a penal colony in the town of Labytnangi, Russia's Yamal.

Sentsov began his hunger strike on May 14, 2018, demanding that Russia free all Ukrainian political prisoners.

Doctors supported his life with the help of a nutrient mix.

In early October, Sentsov announced he had to end his hunger strike due to the deterioration of his health and threats of forced feeding.

Ukrainian Parliament's Commissioner for Human Rights Liudmyla Denisova says Sentsov has not been provided with adequate medical support amid his hunger strike.