KYIV -- Ukrainians mourned the dead as rescuers continued to search the debris for survivors following one of Russia's biggest missile attacks on the Ukrainian capital amid faltering efforts to bring a halt to Russia's 42-month-old war.

Officials declared August 29 a day of mourning in Kyiv for the 23 confirmed killed in the Russian assault a day earlier.

The attack, which involved more than 600 drones and missiles, was the biggest since a major summit nearly two weeks earlier between presidents Vladimir Putin of Russia and Donald Trump of the United States.

US officials had voiced optimism that the face-to-face meeting would lead to a cessation of fighting and a possible meeting between Putin and Ukraine's Volodymyr Zelenskyy.

But Russian officials, including Putin, have signaled virtually no willingness to back off from hard-line demands, which include Ukraine giving up substantial territory.

"Russia is now striking at everyone in the world who wants peace," Zelenskyy said on August 28 in hisnightly video address.

"It is a strike against Ukraine.... And it is also a strike by Russia against President Trump," he said.

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At the White House, spokeswoman Karoline Leavitt said the overnight attacks had frustrated Trump.

"He was not happy about this news, but he was also not surprised. These are two countries that have been at war for a very long time," she told reporters on August 28.

One of the worst-hit sites was in Kyiv's Darnytsya district, where a section of a five-story residential building was directly hit.