The second round of peace talks between Russia and Ukraine is scheduled to take place on Monday at 1 p.m. at the Ciragan Palace in Istanbul, according to an announcement made by the Turkish Ministry of Foreign Affairs on Sunday.

As both sides prepare for negotiations, the situation on the ground has escalated sharply, with Ukraine claiming a large-scale strike on Russian strategic bombers on the eve of the talks.

Ukraine's proposal for peace talks

Ukraine has outlined its demands for a peace deal with Russia ahead of negotiations.

According to the proposal, the process would begin with a minimum 30-day ceasefire, followed by a full exchange of prisoners and the return of Ukrainian children taken to Russian-held areas, ultimately leading to a potential meeting between Ukrainian President Volodymyr Zelenskyy and Russian President Vladimir Putin. The plan was reported on June 1 by Reuters, which reviewed a copy of the document.

Zelenskyy announced on Sunday an updated 14-member Ukrainian delegation for upcoming peace talks, expanding the original group of 12. Defense Minister Rustem Umerov will again lead the delegation, which will include several new figures from Ukraine's military, human rights and legal sectors.

He emphasized the necessity of a future summit between national leaders, stating that only high-level direct dialogue can resolve the core issues of the conflict.

According to Russian Foreign Ministry spokeswoman Maria Zakharova, Russia's delegation in Istanbul will remain unchanged and be led again by Presidential Aide Vladimir Medinsky, who has already arrived in Istanbul.

Russia is bringing a draft memorandum and additional proposals aimed at achieving a ceasefire. Kremlin Press Secretary Dmitry Peskov on May 30, expressed hope that this new round would enable both sides to discuss the draft peace agreement. He noted that while the contents of the memorandum would not be made public, navigation safety in the Black Sea may be included as part of the talks.

Regarding U.S. President Donald Trump's offer to host a trilateral summit, Peskov said the Russian president supports high-level engagements in principle, but only after concrete progress is made in the Istanbul peace talks.

Conflicts intensify on the eve of talks

Ahead of the peace talks in Istanbul, Ukraine and Russia escalated the conflict by blowing up two bridges, attacking nuclear-capable bombers deep in Siberia and striking an army training facility.

On the night of May 31, a bridge collapsed in Russia's Bryansk region, neighboring Ukraine. At least seven people were killed and 69 injured when the highway bridge was blown up over a passenger train heading to Moscow with 388 people on board.

Just hours later, another railway bridge in Kursk collapsed, resulting in a freight train derailment and fire that injured the driver and two assistants. So far, no one has yet claimed responsibility.

The Russian Investigative Committee has launched investigations into both incidents and labeled them as "acts of terrorism." However, a Ukrainian national security official said the incidents were Russian "false flag" operations, designed to "manipulate international opinion" ahead of peace talks.

In a parallel development, Ukraine's Defense Intelligence announced that a Russian military train carrying supplies was blown up in southern Zaporizhzhia Oblast. The agency didn't claim responsibility for it, but said the fight against the military logistics of Russia continues.

Furthermore, late on Sunday, Ukraine's Security Service (SBU) declared that it had launched a special operation against Russian strategic air bases. According to the agency, roughly 34 percent of Russia's nuclear-capable long-range bombers were hit, including key targets in a military base deep in Siberia.

A Ukrainian intelligence official said this is the first such attack so far from the front lines, more than 4,300 kilometers away. The official said the operation involved hiding explosive-laden drones inside the roofs of wooden sheds and loading them onto trucks that were driven to the perimeter of the air bases.

A total of 41 Russian warplanes were hit, the official said. Zelenskyy expressed delight at the "absolutely brilliant outcome," noting 117 drones had been used in the attack. A Ukrainian government official told Reuters that Ukraine did not notify the U.S. of the attack in advance.

In response, a Russian fact-checking site "warfakes" accused Ukraine of exaggerating its achievements. The site claimed that a maximum of two long-range aircraft and an An-12 transport plane were destructed. "Regarding the remaining aircraft, it cannot be said with certainty that their damage cannot be repaired," said the site.

On the Russian side, earlier on Sunday, Russian forces launched a missile strike on a Ukrainian army training facility. According to Ukraine's Army Press Service, the attack resulted in significant casualties, killing 12 soldiers and injured more than 60 others.

With only hours remaining before the second round of Russia-Ukraine peace talks, experts say the core issue on the agenda remains a ceasefire. However, deep divisions persist between the two sides.

Professor Wang Shuo of Beijing Foreign Studies University told China Media Group that the key points of this round largely mirror those of the first. Russia seeks to link any ceasefire to broader demands, including NATO's non-expansion, Ukraine's neutrality, and the lifting of Western sanctions. Ukraine, on the other hand, favors an immediate ceasefire before addressing broader terms, aiming to buy time for its embattled forces.

Wang also emphasizes the fundamental lack of trust between Moscow and Kyiv, warning that while both sides express a willingness to negotiate and international expectations for peace are high, the talks are likely to be difficult and protracted.

(With input from agencies)