KYIV, Ukraine (AP) — Russia unleashed waves of missiles and drones at Ukraine early Monday, killing at least 22 people in attacks that exposed widening gaps in the country’s air defenses more than four years into Moscow’s full-scale invasion, authorities said.

All of the ballistic missiles launched by Russia struck their targets, underscoring Kyiv’s need for more U.S.-made Patriot interceptor missiles — a point Ukrainian President Volodymyr Zelenskyy will likely reiterate at a NATO summit in Ankara, Turkey, this week.

Fifteen people were killed in the capital of Kyiv, which was Russia’s main target, and 56 were injured, according to administrative head Tymur Tkachenko. Another seven people were killed in the wider Kyiv region and 29 were injured, according to Ukraine’s emergency service.

Emergency workers searched for survivors in the rubble of residential high-rises in two locations that suffered direct hits.

Moscow has stepped up attacks on Kyiv in retaliation for Ukraine’s recent long-range strikes, according to the Russian Defense Ministry. Those Ukrainian attacks have caused severe fuel shortages and put pressure on President Vladimir Putin.

On Thursday, a Russian strike killed 31 people in Kyiv, the deadliest attack in the capital this year.

Ukraine’s advances in drone technology have given it an edge in recent months, analysts and Western officials say, striking supply routes behind the front line, stripping the Russian army of momentum on the battlefield and slowing its advance.

But Russia now is exploiting vulnerabilities in Ukraine’s air defenses, which remain heavily reliant on the Patriot missile systems to intercept ballistic missiles it can rarely shoot down. The war in the Middle East has strained the global supply of Patriot interceptors — a shortage now felt keenly in Ukraine.

Ukraine’s air force said Russia fired 351 drones and 68 missiles overnight, targeting mainly Kyiv, and all 29 ballistic missiles struck their targets.

“To intercept ballistics, we need the means for interception,” air force spokesman Yurii Ihnat said on national television. “Russians are certainly using the fact that there is a serious deficit of interceptor missiles now, in Ukraine and the world.”

Ahead of the NATO summit in Turkey, Zelenskyy said Ukrainian forces had performed well against drones and cruise missiles but not against ballistic missiles — a shortfall he blamed on insufficient supplies of interceptors. He urged U.S. and European partners at the summit to bolster Ukraine’s air defense and protect civilians.

“As long as Patriot missiles remain in our allies’ stockpiles, Russia is only encouraged to keep ‘vanquishing’ residential buildings. The United States and Europe have enough strength to stop this terror,” he said on X following the attack.

Russia’s Defense Ministry said any increase in the supply of drones, missiles and ammunition produced in the West “will not go unnoticed and will be countered by a corresponding increase in the number and power of retaliatory strikes by the Russian armed forces on Ukrainian territory.”

Ukraine’s Defense Minister Mykhailo Fedorov said Russia is deliberately ramping up ballistic missile attacks on a scale unseen before, exploiting the acute shortage of Patriot interceptors. “Fewer such missiles are produced worldwide each month than the enemy fires at Ukraine in that same period,” he said.