Washington [US], June 2 (ANI): US Secretary of State Marco Rubio has spoken with his Russian counterpart about ending the Ukraine conflict, as both sides prepare for fresh negotiations in Istanbul.

The diplomatic contact between Rubio and Russian Foreign Minister Sergei Lavrov came as Ukraine and Russia conducted some of the largest drone attacks since the war began nearly three years ago.

A second round of direct peace talks is scheduled to take place in Istanbul on Monday, with Ukrainian negotiators set to present new proposals to Russian representatives.

The US State Department said Rubio had 'reinforced President Trump's call for ongoing direct negotiations between Russia and Ukraine' aimed at achieving lasting peace.

During their conversation, Rubio also offered condolences for casualties from the destruction of two bridges in Russian border regions.

Russian officials said a full investigation would be conducted into the incidents, with results to be made public and those responsible facing 'appropriate consequences'.

Ukraine carried out a significant drone attack on Sunday targeting deep inside Russian territory, destroying dozens of nuclear-capable bombers and other military aircraft.

The operation, which had reportedly been planned for more than a year, involved secretly transporting numerous drones into Russia for the covert mission.

However, Ukraine did not inform the Trump administration beforehand about the strikes, according to reports by CBS and Axios citing unnamed sources. The White House has not commented on the matter.

The timing of the assault was particularly notable, occurring just as diplomatic efforts were intensifying ahead of Monday's peace negotiations.

President Trump, who has pledged to end the Ukraine war quickly, has been putting pressure on both sides to engage in talks.

The president spent Sunday morning playing golf at his club in Sterling, Virginia, alongside professional golfer Bryson DeChambeau.

Trump has previously expressed frustration with Ukrainian President Volodymyr Zelensky, though he has also criticised Russia's invasion.

The diplomatic developments come as fighting continues to rage across multiple fronts, with both Ukraine and Russia conducting intensive drone campaigns against each other's territory.

The Istanbul talks represent the most significant diplomatic engagement between the warring parties in recent months, though previous negotiation attempts have failed to produce lasting agreements. (ANI)