Ukrainian President Volodymyr Zelenskyy said Tuesday he stressed the need for a “powerful missile defense system for Ukraine to prevent Russian terrorist attacks” in talks with NATO’s leader.

The phone call with NATO Secretary General Jens Stoltenberg came ahead of the start of a summit of NATO leaders in Madrid where Ukraine is expected to be among the major topics of discussion.

“At our NATO summit we will step up support for our close partner Ukraine, now and for the longer term,” Stoltenberg tweeted after speaking with Zelenskyy. “NATO allies stand with you.”

Stoltenberg said Monday that the Western military alliance is declaring a sevenfold increase in the number of its troops on standby alert — from 40,000 to more than 300,000.

Rescue crews in central Ukraine worked Tuesday to search for survivors at a shopping center where Russian forces carried out a missile strike on Monday, killing at least 18 people.

Zelenskyy said there were more than 1,000 civilians inside the mall in the city of Kremenchuk at the time of the attack, which he called “calculated.”

“This is not an accidental hit, this is a calculated Russian strike exactly onto this shopping center,” Zelenskyy said Monday in his nightly video address. He added that the strike “is one of the most daring terrorist attacks in European history.”

Zelenskyy had said earlier on Telegram that the number of casualties is “impossible to even imagine” and said the shopping center, in a city 300 kilometers southeast of the capital, Kyiv, was “no danger to the Russian army, no strategic value.”

U.S. Secretary of State Antony Blinken tweeted, “The world is horrified by Russia’s missile strike today, which hit a crowded Ukrainian shopping mall — the latest in a string of atrocities. We will continue to support our Ukrainian partners and hold Russia, including those responsible for atrocities, to account.”

U.N. spokesperson Stephane Dujarric called the attack “deplorable” and said the U.N. Security Council would meet Tuesday at Ukraine’s request following the strike.

Group of Seven

The missile strike took place as the Group of Seven leading industrialized economies met in Germany’s Bavarian Alps and pledged continued support for Ukraine.

Leaders from the group called Monday’s missile strike “abominable” and said in a joint statement, “We stand united with Ukraine in mourning the innocent victims of this brutal attack.”

The United States and the other members of the G-7 on Monday imposed new sanctions against Russia for its four-month invasion of Ukraine.

These include measures to cut off Moscow from materials and services needed by its industrial and technology sectors.

The White House said the United States will commit $7.5 billion as part of a G-7 effort to help Ukraine cover its short-term budget needs, and that the governments are making “an unprecedented, long-term security commitment to providing Ukraine with financial, humanitarian, military and diplomatic support as long as it takes.”

In a joint communique, the G-7 said, “We remain appalled by and continue to condemn the brutal, unprovoked, unjustifiable and illegal war of aggression against Ukraine by Russia and aided by Belarus. We condemn and will not recognize Russia’s continued attempts to redraw borders by force.”

Zelenskyy addressed the conference by video link earlier Monday and requested more weapons as well as help exporting grain past Russian blockades.

Some information for this report came from The Associated Press and Reuters.