By Rhea Mogul, Amy Woodyatt, Matt Meyer, Mike Hayes and Maureen Chowdhury, CNN
Maxar satellite images captured the damage to the Kerch Strait bridge Saturday, shortly after an explosion rocked the only direct road and rail connection between annexed Crimea and mainland Russia.
The blast caused parts of the bridge to collapse, though Russian transportation officials restarted rail service and allowed vehicles to use some undamaged portions of the roadway by Saturday evening.
From CNN's Sharon Braithwaite
The UN's nuclear watchdog condemned new shelling near Ukraine's Zaporizhzhia nuclear power plant, which just disconnected the plant from Ukraine's power grid, according to its operator.
The resumed shelling is "tremendously irresponsible," International Atomic Energy Agency Director General Rafael Grossi said Saturday in a press release.
The last power line connecting the plant to Ukraine’s power grid was damaged and disconnected Saturday due to attacks by Russian forces, according to the Ukrainian nuclear operator Energoatom. The plant is now relying on diesel generators.
“The resumption of shelling, hitting the plant’s sole source of external power, is tremendously irresponsible. The Zaporizhzhia Nuclear Power Plant must be protected,” Grossi said on Saturday.
"All the plant’s safety systems continue to receive power and are operating normally, the IAEA experts were informed by senior Ukrainian operating staff at the site,” he added in the release.
"Although the six reactors are in cold shutdown, they still require electricity for vital nuclear safety and security functions. The plant’s diesel generators each have sufficient fuel for at least ten days. ZNPP engineers have begun work to repair the damaged 750 kV power line," according to the release.
Grossi stressed that the plant "must be protected” and added that he will "soon travel to the Russian Federation, and then return to Ukraine, to agree on a nuclear safety and security protection zone around the plant. This is an absolute and urgent imperative.”
What Russian officials say: The plant can be put back into operation, said Vladimir Rogov, who is a senior pro-Russian official in the regional Zaporizhzhia government.
"Now the nuclear power plant has been switched back to the emergency mode of operation. The last power line that connected it with the right bank, with the territories controlled by [Ukrainian President Volodymyr] Zelensky's regime, has been cut. For now, the nuclear power plant can only be powered by diesel generators, and this is an unusual means," Rogov said while speaking to the pro-Kremlin "Soloviev Live" show on Saturday.
"We have every possibility to restore the nuclear power plant and put it into operation," he added.
Analysis from CNN's Nick Paton Walsh
The Crimean bridge explosion accelerates the strategic choices Russian President Vladimir Putin must make about Russia’s occupation of southern Ukraine.
This entire presence was already poorly supplied, managed and in retreat. Rickety ferry crossings in bad weather or highly dangerous air cargo flights may now be needed to bolster military shipments into Crimea and toward the frontlines.
Ukraine has been targeting Russia' aging transport dependencies — particularly its reliance on rail — with slow, patient accuracy. First Izium, which led to the collapse around Kharkiv. Then Lyman, which is leading to the erosion of Russia’s control of Donetsk and Luhansk. And now the Kerch Strait bridge, which had become so vital to everything that Russia is trying to hold on to in the south.
Putin now faces a series of expedited and painful decisions, all of which will severely belie his continued poker-face of pride and bombast toward the gathering signs of slow defeat.
To the west of the Dnieper river, his army in Kherson is besieged by fast-moving Ukrainian forces. Putin's troops are already in retreat, partially owing to the same poor resupply that will be accentuated by the Kerch blast.
They are again cut off from this faltering supply line by another series of damaged or targeted bridges across the Dnieper. Over the past week, they have already fallen back over 500 square kilometers (about 193 square miles).
Can Moscow sustain this force over two damaged supply routes? A precarious presence has perhaps overnight become near-impossible.
The second point of decision relates to Crimea. Putin now faces the difficult choice of fortifying it further with depleted forces who face resupply issues, or partially withdrawing his military to ensure their significant resources on the peninsula do not get cut off.
Putin must choose between feeding his larger ambitions with a dwindling chance of success or consolidating forces around an objective he has a greater chance of achieving.
One carries the risk of catastrophic collapse, for his entire brutal adventure into Ukraine — and quite possibly, his rule. The second leaves him with an immediate loss of face, but a stronger chance of sustaining the occupation of smaller parts of Ukraine.