KYIV, Ukraine (AP) — Russia unleashed a lethal barrage of strikes against multiple Ukrainian cities Monday, smashing civilian targets including downtown Kyiv where at least six people were killed amid burnt-out cars and shattered buildings that brought back into focus the grim reality of war after months of easing tensions in the capital.

Police said a total of at least 10 people were killed and around 60 others were wounded in the morning attacks across Ukraine. The country’s Emergency Service said nine people were killed. The conflicting numbers couldn’t immediately be reconciled.

Russian President Vladimir Putin, whose military invaded neighboring Ukraine on Feb. 24, said the strikes were in retaliation for what he called Kyiv’s “terrorist” actions — a reference to Ukraine’s attempts to repel Moscow’s invasion forces and cripple their supply lines.

The actions he referred to include an attack last weekend on a key bridge, prized by the Kremlin, between Russia and the annexed Crimean Peninsula.

Putin vowed a “tough” and “proportionate” response should Ukraine carry out further attacks that threaten Russia’s security.

“No one should have any doubts about it,” he said.

Monday’s intense, hours-long attack by Russia marked a sudden military escalation in its assault on Ukraine. It came a day after Putin called the explosion Saturday on the huge bridge connecting Russia to its annexed territory of Crimea a “terrorist act” masterminded by Ukrainian special services.

Putin, speaking in a video call with members of Russia’s Security Council, said the Russian military launched “precision weapons” from the air, sea and ground to target key energy and military command facilities.

The missile strikes marked the biggest and most widespread Russian attacks in months. Putin, whose partial mobilisation order earlier this month triggered an exodus of hundreds of thousands of men of fighting age from Russia, stopped short of declaring martial law or a counterterrorism operation as many had expected.

But the sustained barrage on major cities hit residential areas and critical infrastructure facilities alike, portending a major surge in the war amid a successful Ukrainian counteroffensive in recent weeks and raising questions about how “precise” Russia’s targeting is.

Moscow’s war in Ukraine is approaching its eight-month milestone, and the Kremlin has been reeling from humiliating battlefield setbacks in areas of eastern Ukraine it is trying to annex.

Blasts struck in the capital’s Shevchenko district, a large area in the center of Kyiv that includes the historic old town as well as several government offices, Mayor Vitali Klitschko said.

Some of the strikes hit near the government quarter in the symbolic heart of the capital, where Parliament and other major landmarks are located. A glass tower housing offices was significantly damaged, most of its blue-tinted windows blown out.

Residents were seen on the streets with blood on their clothes and hands. A young man wearing a blue jacket sat on the ground as a medic wrapped a bandage around his head. A woman with bandages wrapped around her head had blood all over the front of her blouse. Several cars were also damaged or completely destroyed. Air raid sirens sounded repeatedly across the country and in Kyiv.

Ukrainian President Volodymyr Zelenskyy said Russian forces launched dozens of missiles and Iranian-built drones against Ukraine.

The General Staff of the Ukraine Armed Forces said 75 missiles were fired against Ukrainian targets, with 41 of them neutralised by air defenses.

The targets were civilian areas and energy facilities in 10 cities, Zelenskyy said in a video address. “(The Russians) chose such a time and such targets on purpose to inflict the most damage,” Zelenskyy said.

The morning strikes sent Kyiv residents back into bomb shelters for the first time in months. The city’s subway system stopped train services and made the stations available once more as places for refuge.

While air raid sirens have continued throughout the war in Ukraine’s major cities across the country, in Kyiv and other areas where there have been months of calm many Ukrainians had begun to ignore their warnings and go about their normal business.

That changed on Monday morning. The attacks arrived in Kyiv at the start of the morning rush hour, when commuter traffic was beginning to pick up. At least one of the vehicles struck near the Kyiv National University appeared to be a commuter minibus, known as a “marshrutka” and which is a popular albeit often crowded alternative to the city’s bus and metro routes.

Nearby, at least one strike landed in the popular Shevchenko Park, leaving a large hole near a children’s playground.

Among the targets hit was a pedestrian bridge known as the Klitschko bridge — a landmark in central Kyiv with its glass panels. Closed-circuit television footage shared by an adviser to Ukraine’s interior minister showed a huge explosion as the bridge was apparently targeted. A man seen on the bridge just before the explosion is seen running away after the blast.

Lesia Vasylenko, a member of Ukraine’s parliament, tweeted a photo showing that at least one explosion occurred near the main building of the Kyiv National University in central Kyiv.

Elsewhere, Russia targeted civilian areas and energy infrastructure as air raid sirens sounded in every region of Ukraine, except Russia-annexed Crimea, for four straight hours.

Associated Press journalists in Dnipro city saw the bodies of multiple people killed at an industrial site on the city’s outskirts. Windows in the area had been blown out and glass littered the street. A telecommunications building was hit.

Ukrainian media also reported explosions in a number of other locations, including the western city of Lviv, which has been a refuge for many people fleeing the fighting in the east, as well as in Kharkiv, Ternopil, Khmelnytskyi, Zhytomyr and Kropyvnytskyi.

Kharkiv was hit three times, Mayor Ihor Terekhov said. The strikes knocked out the electricity and water supply. Energy infrastructure was also hit in Lviv, regional Gov. Maksym Kozytskyi said.

Three cruise missiles launched against Ukraine from Russian ships in the Black Sea crossed Moldova’s airspace, the country’s Foreign Affairs Minister Nicu Popescu complained.

A day earlier, Putin had called the attack on the Kerch Bridge to Crimea a terrorist act carried out by Ukrainian special services. In a meeting Sunday with the chairman of Russia’s Investigative Committee, Putin said “there’s no doubt it was a terrorist act directed at the destruction of critically important civilian infrastructure.”

The Kerch Bridge is important to Russia strategically, as a military supply line to its forces in Ukraine, and symbolically, as an emblem of its claims on Crimea. No one has claimed responsibility for damaging the 12-mile (19-kilometre) -long bridge, the longest in Europe.

Amid the onslaught, Zelenskyy said on his Telegram account that Russia is “trying to destroy us and wipe us off the face of the earth.”

The attacks appeared set to bring a fresh bout of international condemnation for Russia.

German Chancellor Olaf Scholz’s spokesman, Steffen Hebestreit, said the Group of Seven industrial powers will hold a videoconference Tuesday on the situation which Zelenskyy will address. Germany currently chairs the G-7.

The attacks brought a chorus of outrage in Europe. French President Emanuel Macron expressed “extreme concern, as the strikes caused civilian casualties” and renewed his pledge of more military aid for Ukraine.

British Foreign Secretary James Cleverly tweeted that “Russia’s firing of missiles into civilian areas of Ukraine is unacceptable.”

Ukrainian Foreign Minister Dmytro Kuleba broke off his Africa tour and headed back to Ukraine, tweeting that the attacks represented “terror on peaceful Ukrainian cities.”

Some feared Monday’s attacks may just be the first salvo in a renewed Russian offensive. Ukraine’s Ministry of Education announced that all schools in Ukraine must switch to online classes at least until the end of this week.

In an ominous move, Belarusian President Alexander Lukashenko announced Monday that he and Putin have agreed to deploy a joint “regional grouping of troops” amid the escalation of fighting in Ukraine. He offered no details as to where the grouping will be deployed, when and what for.

Lukashenko repeated his claims that Ukraine is plotting an attack on Belarus, sparking fears the stage is being set for preemptive action by Minsk.