Ukrainian President Volodymyr Zelenskyy is due to address the leaders of the Group of Seven nations during a virtual meeting Tuesday that follows a series of deadly Russian missile strikes on Ukraine’s capital and other cities located across the country.

Zelenskyy said Monday that Ukraine “cannot be intimidated,” and rather than instill fear, Russia’s attacks made “the whole world take notice.”

“We will do everything to strengthen our armed forces,” Zelenskyy said. “We will make the battlefield more painful for the enemy.”

The Ukrainian leader tweeted after a phone call with U.S. President Joe Biden that air defense was his top priority, and that he was looking to the United States for leadership on a “tough stance” from the G-7 as it considers its response to Russia’s attacks.

Biden and Western allies were quick to condemn the attacks and vowed to continue to send military aid to Ukraine’s forces to help fend off Moscow’s invasion, now in its eighth month.

A White House statement said Biden told Zelenskyy the United States would provide advanced air defense systems.

Biden said in a statement earlier Monday that Russia’s latest missile launches “once again demonstrate the utter brutality of Russian President Vladimir Putin’s illegal war on the Ukrainian people.

“These attacks only further reinforce our commitment to stand with the people of Ukraine for as long as it takes,” he said. “Alongside our allies and partners, we will continue to impose costs on Russia for its aggression, hold Putin and Russia accountable for its atrocities and war crimes, and provide the support necessary for Ukrainian forces to defend their country and their freedom.”

Russian attack includes 84 missiles, 24 drones    

Putin called Monday’s missile attack a “massive strike” against Ukraine in response to the recent destructive attack on the bridge linking Crimea to the Russian mainland.

The Ukrainian military said Russia launched a barrage of 84 cruise missiles and 24 drones, hitting at least 14 areas of the country, and killing at least 14 people. Most of the attacks on Kyiv hit the center of the city, killing at least six people there and wounding 12 others in populated areas, including parks and tourist sites.

The attacks also caused a blackout in much of the country, with hundreds of thousands of people without power Monday night.

European Commission President Ursula von der Leyen said she was “shocked and appalled by the vicious attacks on Ukrainian cities. Putin’s Russia has again shown the world what it stands for: brutality and terror.”

Putin told a meeting of his security council that the strikes targeted Ukraine’s energy, military and communications infrastructure, and that they were in response to an attack Saturday on a bridge linking Russia to Crimea, the Ukrainian peninsula Moscow illegally seized in 2014.

“It is obvious that the Ukrainian secret services ordered, organized and carried out the terrorist attack aimed at destroying Russia’s critical civilian infrastructure,” Putin said.

Aside from Kyiv, explosions were also reported in the western city of Lviv, the southeast city of Dnipro and the eastern city of Kharkiv. Ukraine’s military said it shot down 56 of the Russian aerial targets.

“Unacceptable escalation”

United Nations Secretary-General Antonio Guterres was “deeply shocked” by the Russian attacks, his spokesman said. “This constitutes another unacceptable escalation of the war and, as always, civilians are paying the highest price,” the spokesman added. Guterres later talked with Zelenskyy, saying they agreed that the world must react to Russia’s attack as soon as possible.

Ukraine has strongly suggested its security agents carried out the truck bomb attack on the bridge but has not publicly claimed responsibility. The bridge has been a major supply route for Russian operations in southern Ukraine.

Putin said any continued “terrorist attacks” by Ukraine on Russia would be met with a “tough and proportionate” response.

Ukrainian Foreign Minister Dmytro Kuleba contended the bridge attack did not provoke Putin “to unleash missile terror.”

“Russia had been constantly hitting Ukraine with missiles before the bridge, too,” Kuleba tweeted. “Putin is desperate because of battlefield defeats and uses missile terror to try to change the pace of war in his favor.”

Kyiv was last attacked in June. Once under pressure from advancing Russian forces, Kyiv had been relatively calm for months as fighting raged in eastern and southern Ukraine.

Some information for this story came from The Associated Press, Agence France-Presse and Reuters.