KYIV, April 26 - Ukraine on Thursday marked 32 years since Chernobyl, the world's worst civilian nuclear accident, saying it would "remain an open wound in the hearts of millions."

The accident spread radioactive fallout across Europe in 1986, particularly contaminating Ukraine, Russia and Belarus.

"Chernobyl will always remain an open wound in the heart of our country, in the hearts of millions of people," President Petro Poroshenko wrote on Facebook.

In Ukraine's capital, Kyiv, hundreds of people marched at midnight to the Memorial Hill of Chernobyl Heroes where they laid flowers and lit candles. At 1 a.m. on April 26, an Orthodox service and a prayer to commemorate Chernobyl victims were performed at the site, RFE/RL reported.

The Ukrainian government has been working to turn the Chernobyl exclusion zone into massive solar power plant park that will generate electricity.

"Today, we have to do everything to prevent a repetition of that tragedy... the Chernobyl zone must now become a place of new technologies, a territory of changes,” Poroshenko wrote.

In Belarus, the opposition plans to hold a march in Minsk known as the "Chernobyl Path" later on April 26.

The march has been held in the Belarusian capital since 1988 to commemorate the disaster in neighboring Ukraine, which also contaminated large swaths of territory in Belarus.

An explosion on April 26, 1986, blew the roof off the building housing a nuclear reactor and spewed a cloud of radioactive material high into the air -- drifting across Ukraine's borders into Russia, Belarus, and across large parts of Europe.

About 30 people died in the immediate aftermath and thousands more are feared to have died in the years that followed from the effects of the disaster -- mainly exposure to radiation.

On April 25, the Vienna-based UN Scientific Committee on the Effects of Atomic Radiation said that around 20,000 thyroid cancer cases were registered between 1991 and 2015 in the area surrounding the reactor, which takes in all of Ukraine and Belarus, as well parts of Russia.

The UN scientists said that since the accident, 1-in-4 thyroid cancer cases have been caused by radiation in the region.

In November 2016, a huge arch was placed over the stricken reactor to prevent further leaks of radiation. The project -- funded by the European Bank for Reconstruction and Development -- cost $1.6 billion. (nr/rfe/ez)