On the eve of peace talks, Ukraine and Russia sharply ramped up the war with one of the biggest drone battles of their conflict, a Russian highway bridge blown up over a passenger train and an ambitious attack on nuclear-capable bombers deep in Siberia.

After days of uncertainty over whether or not Ukraine would even attend, President Volodymyr Zelenskiy said Defence Minister Rustem Umerov would sit down with Russian officials at the second round of direct peace talks in Istanbul on Monday.

The talks, proposed by President Vladimir Putin, have so far yielded the biggest prisoner exchange of the war - but no sense of any consensus on how to halt the fighting.

Amid talk of peace, though, there was much war.

At least seven people were killed and 69 injured when a highway bridge in Russia’s Bryansk region, neighbouring Ukraine, was blown up over a passenger train heading to Moscow with 388 people on board. No one has yet claimed responsibility.

Ukraine attacked Russian nuclear-capable long-range bombers at a military base deep in Siberia on Sunday, the first such attack so far from the front lines more than 4,300 km (2,670 miles) away. A Ukrainian intelligence official said 40 Russian warplanes were struck.

Russia launched 472 drones at Ukraine overnight, Ukraine’s air force said, the highest nightly total of the war so far. Russia had also launched seven missiles, the air force said.

Russia said it had advanced deeper into the Sumy region of Ukraine, and open source pro-Ukrainian maps showed Russia took 450 square km of Ukrainian land in May, its fastest monthly advance in at least six months.

US President Donald Trump has demanded Russia and Ukraine make peace and he has threatened to walk away if they do not - potentially pushing responsibility for supporting Ukraine onto the shoulders of European powers - which have far less cash and much smaller stocks of weapons than the United States.

According to Trump envoy Keith Kellogg, the two sides will in Turkey present their respective documents outlining their ideas for peace terms, though it is clear that after three years of intense war, Moscow and Kyiv remain far apart.

Putin ordered tens of thousands of troops to invade Ukraine in February 2022 after eight years of fighting in eastern Ukraine between Russian-backed separatists and Ukrainian troops. The United States says over 1.2 million people have been killed and injured in the war since 2022.

Trump has called Putin “crazy” and berated Zelenskiy in public in the Oval Office, but the US president has also said that he thinks peace is achievable and that if Putin delays then he could impose tough sanctions on Russia.

In June last year, Putin set out his opening terms for an immediate end to the war: Ukraine must drop its NATO ambitions and withdraw all of its troops from the entirety of the territory of four Ukrainian regions claimed and mostly controlled by Russia.

Ukrainian negotiators in Istanbul will present to the Russian side a proposed roadmap for reaching a lasting peace settlement, according to a copy of the document seen by Reuters.

According to the document, there will be no restrictions on Ukraine’s military strength after a peace deal is struck, no international recognition of Russian sovereignty over parts of Ukraine taken by Moscow’s forces, and reparations for Ukraine.

The document also stated that the current location of the front line will be the starting point for negotiations about territory.

Russia currently controls a little under one fifth of Ukraine, or about 113,100 square km, about the same size as the US state of Ohio.