Kyiv, Mar 5 (AP): Russian troops has seized the biggest nuclear power plant in Europe after a middle-of-the-night attack that set it on fire and briefly raised worldwide fears of a catastrophe in the most chilling turn yet in Moscow's invasion of Ukraine.

Firefighters put out the fire after the Friday attack, and no radiation was released, UN and Ukrainian officials said, as Russian forces pressed on with their week-old offensive on multiple fronts and the number of refugees fleeing the country eclipsed 1.2 million.

While the vast Russian armoured column threatening Kyiv remained stalled outside the capital, President Vladimir Putin's military has launched hundreds of missiles and artillery attacks on cities and other sites around the country, and made significant gains on the ground in the south in an apparent bid to cut off Ukraine's access to the sea.

In the attack on the Zaporizhzhia nuclear plant in the southeastern city of Enerhodar, the chief of the UN's International Atomic Energy Agency, Rafael Mariano Grossi, said a Russian “projectile” hit a training centre, not any of the six reactors.

The attack triggered global alarm and fear of a catastrophe that could dwarf the world's worst nuclear disaster, at Ukraine's Chernobyl in 1986. In an emotional nighttime speech, Ukrainian President Volodymyr Zelenskyy said he feared an explosion that would be “the end for everyone. The end for Europe. The evacuation of Europe.” But nuclear officials from Sweden to China said no radiation spikes had been reported, as did Grossi.

Authorities said that Russian troops had taken control of the overall site but that the plant staff continued to run it. Only one reactor was operating, running at 60 per cent of capacity, Grossi said in the aftermath of the attack.

Two people were injured in the fire, Grossi said. Ukraine's state nuclear plant operator Enerhoatom said three Ukrainian soldiers were killed and two wounded.

In the US, Pentagon spokesman John Kirby said the episode “underscores the recklessness with which the Russians have been perpetrating this unprovoked invasion.” At an emergency meeting of the UN Security Council, Ukraine's UN ambassador, Sergiy Kyslytsya, said the fire broke out as a result of Russian shelling of the plant and accused Moscow of committing “an act of nuclear terrorism.” Without producing evidence, Russian Defense Ministry spokesman Igor Konashenkov claimed that a Ukrainian “sabotage group” had set the fire at Zaporozhizhia.

The crisis at Zaporizhzhia unfolded after Grossi earlier in the week expressed grave concern that the fighting could cause accidental damage to Ukraine's 15 nuclear reactors at four plants around the country.

Atomic safety experts said a war fought amid nuclear reactors represents an unprecedented and highly dangerous situation.

“These plants are now in a situation that few people ever seriously contemplated when they were originally built,” said Edwin Lyman of the Union of Concerned Scientists in Washington. "No nuclear plant has been designed to withstand a potential threat of a full-scale military attack.” Dr Alex Rosen of International Physicians for the Prevention of Nuclear War said the incident was probably the result of military units overestimating the precision of their weapons, given that the prevailing winds would have carried any radioactive fallout straight toward Russia.

“Russia cannot have any interest in contaminating its own territory,” he said. He said the danger comes not just from the reactors but from the risk of enemy fire hitting storage facilities that hold spent fuel rods.

In the wake of the attack, Zelenskyy appealed again to the West to enforce a no-fly zone over his country. But NATO Secretary-General Jens Stoltenberg ruled out that possibility, citing the risk of a much wider war in Europe. He said that to enforce a no-fly zone, NATO planes would have to shoot down Russian aircraft.

“We understand the desperation, but we also believe that if we did that, we would end up with something that could end in a full-fledged war in Europe,” Stoltenberg said.

A round of talks between Russia and Ukraine yielded a tentative agreement Thursday to set up safe corridors to evacuate citizens and deliver food and medicine. But the necessary details still had to be worked out.

The UN human rights office said 331 civilians had been confirmed killed in the invasion but that the true number is probably much higher.

Appearing on video in a message to antiwar protesters in several European cities, Zelenskyy continued to appeal for help.

“If we fall, you will fall,” he said. “And if we win, and I'm sure we'll win, this will be the victory of the whole democratic world. This will be the victory of our freedom. This will be the victory of light over darkness, of freedom over slavery.” Facing worldwide indignation over the invasion, Russia sought to crack down on the flow of information at home.

Putin signed a law making it a crime to intentionally spread what is deemed to be fake news. Russians could get up to 15 years in prison for disseminating information that goes against the official government line on the war.

Russian authorities also blocked all access to Facebook and Twitter and raided the offices of human rights organizations. (AP) VN VN

(This story is published as part of the auto-generated syndicate wire feed. No editing has been done in the headline or the body by ABP Live.)