By MEHMET GUZEL, Associated Press

ISTANBUL (AP) — Delegations from Russia and Ukraine met Monday in Turkey for their second round of direct peace talks in just over two weeks, although expectations were low for any significant progress on ending the3-year-old war after a string of stunning attacks over the weekend.

Kyiv officials said a surprise drone attack Sunday destroyed more than 40 warplanes at air bases deep inside Russia, including the remote Arctic, Siberian and Far East regions more than 4,300 miles from Ukraine.

The complex and unprecedented raid, which struck simultaneously in three time zones, took over a year and a half to prepare and was “a major slap in the face for Russia’s military power,” said Vasyl Maliuk, the head of the Ukrainian security service who led its planning.

Ukrainian President Volodymyr Zelenskyy called it a “brilliant operation” that would go down in history. The operation destroyed or heavily damaged nearly a third of Moscow’s strategic bomber fleet, according to Ukrainian officials.

Russia on Sunday fired the biggest number of drones — 472 — at Ukraine since its full-scale invasion in 2022, Ukraine’s air force said, in an apparent effort to overwhelm air defenses. That was part of a recently escalating campaign of strikes in civilian areas of Ukraine.

Hopes not high for the peace talks

In the aftermath of those strikes, Turkish Foreign Minister Hakan Fidan chaired the peace talks at Istanbul’s Ciragan Palace, a residence dating from the Ottoman Empire.

The talks aim to discuss both sides’ ceasefire terms, he said, adding that “the whole world’s eyes are focused on the contacts and discussions you will have here.”

U.S.-led efforts to push the two sides into accepting a ceasefire have so far failed. Ukraine accepted that step, but the Kremlin effectively rejected it.

The Ukrainian delegation was led by Defense Minister Rustem Umerov, while Vladimir Medinsky, an aide to Russian President Vladimir Putin, headed the Kremlin team.

The Russian and Ukrainian delegations, each numbering more than a dozen people, sat at a U-shaped table across from each other with Turkish officials between them. Many of the Ukrainians wore military fatigues.

Recent comments by senior officials in both countries indicate they remain far apart on the key conditions for stopping the war.

The Institute for the Study of War, a Washington-based think tank, said Sunday that “Russia is attempting to delay negotiations and prolong the war in order to make additional battlefield gains.”

The relentless fighting has frustrated U.S. President Donald Trump’s goal of bringing about a quick end to the war. A week ago, he expressed impatience with Putin as Moscow pounded Kyiv and other Ukrainian cities with drones and missiles for a third straight night. Trump said on social media that Putin “has gone absolutely CRAZY!”

A round of renewed direct talks, held May 16, also in Istanbul, ended after less than two hours. While both sides agreed on a large prisoner swap, there was no breakthrough.

Ukraine upbeat after strikes on air bases

Ukraine was triumphant after targeting the distant Russian air bases. The official Russian response was muted, with the attack getting little coverage on state-controlled television. Russia-1 TV channel on Sunday evening spent a little over a minute on it with a brief Defense Ministry statement read out before images shifted to Russian drone strikes on Ukrainian positions.

Zelenskyy said the setbacks for the Kremlin would help force it to the negotiating table, even as its pursues a summer offensive on the battlefield.

“Russia must feel what its losses mean. That is what will push it toward diplomacy,” he said Monday in Vilnius, Lithuania, meeting with leaders from the Nordic nations and countries on NATO’s eastern flank.

Ukraine has occasionally struck air bases hosting Russia’s nuclear capable strategic bombers since early in the war, prompting Moscow to redeploy most of them to the regions farther from the front line.

Because Sunday’s drones were launched from trucks close to the bases in five Russian regions, military defenses had virtually no time to prepare for them.

Many Russian military bloggers chided the military for its failure to build protective shields for the bombers despite previous attacks, but the large size of the planes makes that challenging.

The attacks were “a big blow to Russian strategic airpower” and exposed significant vulnerabilities in Moscow’s military capabilities, said Phillips O’Brien, a professor of strategic studies at the University of St. Andrews in Scotland.

Edward Lucas, a senior fellow at the Washington-based Center for European Policy Analysis, called it “the most audacious attack of the war” and “a military and strategic game-changer.”

“Battered, beleaguered, tired, and outnumbered, Ukrainians have, at minimal cost, in complete secrecy, and over vast distances, destroyed or damaged dozens, perhaps more, of Russia’s strategic bombers,” he said.

Front-line fighting and shelling grinds on

Zelenskyy said that “if the Istanbul meeting brings nothing, that clearly means strong new sanctions are urgently, urgently needed” against Russia.

International concerns about the war’s consequences, as well as trade tensions, drove Asian share prices lower Monday while oil prices surged.

Fierce fighting has continued along the roughly 620-mile front line, and both sides have hit each other’s territory with deep strikes.

Russian forces shelled Ukraine’s southern Kherson region, killing three people and injuring 19 others, including two children, regional officials said Monday.

Also, a missile strike and shelling around the southern city of Zaporizhzhia, killing five people and injured nine others, officials said.

Russian air defenses downed 162 Ukrainian drones over eight Russian regions overnight, as well as over the Crimean Peninsula, Russia’s Defense Ministry said Monday. Moscow illegally annexed the peninsula in 2014,Crimea,

Ukrainian air defenses damaged 52 out of 80 drones launched by Russia overnight, the Ukrainian air force said.

Associated Press writers Suzan Frazer in Ankara, Turkey; Hanna Arhirova in Kyiv, Ukraine, and Geir Moulson in Berlin contributed.