Tuesday's Orthodox service began at 1:23 a.m. local time, the time when the blast occurred from the nuclear complex on April 26, 1986, spraying nuclear fallout over Europe and Russia and forcing hundreds from their homes. The incident is used on the international nuclear incident scale to mark the most severe of accidents.

From The Associated Press: 

Russian Orthodox Patriarch Kirill led the nighttime service near a monument to firefighters and cleanup workers who died soon after the accident from acute radiation poisoning.

"The world had not known a catastrophe in peaceful times that could be compared to what happened in Chernobyl," said Kirill, who was accompanied by Ukraine's Prime Minister Mykola Azarov and other officials.

"It's hard to say how this catastrophe would have ended if it hadn't been for the people, including those whose names we have just remembered in prayer," he said in an emotional tribute to the workers sent to the Chernobyl plant immediately after one of its reactors exploded to try to contain the contamination.

The explosion that erupted from the Ukranian nuclear plant released an amount of radiation equal to almost 400 atomic bombs dropped on Japan by the U.S. at the end of World War II. According to the World Health Organization, almost 600,000 people were affected.

It wasn't just victims who commemorated the 25th anniversary of the accident Tuesday morning. Responders who were first on the scene also remembered when it was like 25 years ago.

From USA Today:

Natalia Manzurova, 59, arrived in Chernobyl just nine days after the April 26, 1986, explosion at the nuclear power plant in Ukraine created a radiation cloud that stretched across Europe.

She says that at the time, she and other experts in the region had no idea how much radiation had been released in the nuclear disaster at reactor No. 4 of the Chernobyl Nuclear Power Plant.

Manzurova has been marking the 25th anniversary of the explosion with speaking engagements — including one in Washington earlier this month — aimed at raising awareness of the potential consequences of nuclear energy, which March’s nuclear disaster in Fukushima Prefecture, Japan brought back to the forefront.

Manzurova, a nuclear engineer who was called to Chernobyl from her job in Ozersk, Russia, spent four and a half years studying the effect of the radiation on the environment in Chernobyl, and helping cleanup workers, or liquidators.

She says that she would work in the zone 20 days and then go home for 10, and that she experienced many side effects.

“I would get huge headaches and nose bleeds,” says Manzurova, who was later diagnosed with thyroid cancer she attributes to that experience.

The World Health Organization also said last week that as many as 4,000 more cancer deaths than average in the exposed population may be reported after the full toll is measured.