Russia and Ukraine have agreed on the need for humanitarian corridors to deliver aid and help civilians exit besieged Ukrainian cities, in the first apparent sign of progress in talks between the warring sides.

Russian negotiator Vladimir Medinsky reported "substantial progress” at Thursday’s talks –  the second round of negotiations since Russia launched its invasion of Ukraine – saying the "main issue that we settled today is the salvation of people, civilians who have found themselves in a zone of military clashes”.

However, he did not indicate when the safe corridors may be established.

The tentative agreement, reached in Belarus, came as Russian forces continued to surround and attack Ukrainian cities, including the capital, Kyiv, and the second-biggest city of Kharkiv.

Thousands are thought to have died or been wounded in the eight-day conflict, while more than one million people have fled the fighting in what the United Nations has called the swiftest exodus of refugees this century.

Ukraine’s negotiator, Mykhailo Podolyak, said the two sides have agreed to set up "communication and cooperation lines” as soon as possible to facilitate the evacuation of civilians.

A temporary halt to fighting in select locations was also possible, he said.

"That is, not everywhere, but only in those places where the humanitarian corridors themselves will be located, it will be possible to cease fire for the duration of the evacuation,” he said.

The two sides also saw eye-to-eye on the delivery of medicines and food to the places where the fiercest fighting was taking place, Podolyak said, adding that the two sides will continue the work at "the third round at the earliest possible time”.

The delegations also discussed "the military aspect” and "a future political settlement of the conflict”, according to the Russian negotiators. The third round will take place "in the coming days”, also in Belarus, they said.

John Herbst, a former United States ambassador to Ukraine, called the agreement on humanitarian corridors a "positive sign”.

"If the political will is there to make it happen, it could be a matter of one day or two days,” he told Al Jazeera.

"It’s interesting that even as Moscow is dictating unconditional surrender terms to the conflict, they are willing to consider this. I think that may be because of the pounding they are receiving globally for their barbarous campaign,” he added.