People attend a funeral ceremony for four of the Ukrainian military servicemen, who were killed during an airstrike in a military base in Yarokiv, in a church in Lviv, Ukraine, Tuesday, March 15, 2022. At least 35 people were killed and many wounded in Sunday's Russian missile strike on a military training base near Ukraine's western border with NATO member Poland. (AP Photo/Bernat Armangue)

KYIV, Ukraine (AP) — Ukraine said it saw possible room for compromise Tuesday in talks with Russia, while Moscow’s forces stepped up their bombardment of Kyiv, and an estimated 20,000 civilians fled the desperately encircled port city of Mariupol by way of a humanitarian corridor.

The fast-moving developments on the diplomatic front and on the ground came on the 20th day of Russia’s invasion, as the number of Ukrainians fleeing the country amid Europe’s heaviest fighting since World War II eclipsed 3 million.

A top Ukrainian negotiator, presidential adviser Mykhailo Podolyak, described the latest round of talks with the Russians, held via videoconference, as “very difficult and sticky” and said there were “fundamental contradictions” between the two sides, but added that “there is certainly room for compromise.” He said the talks will continue Wednesday.

Earlier in the day, another aide to Ukrainian President Volodymir Zelenskyy, Ihor Zhovkva, struck a more optimistic note, saying that the negotiations had become “more constructive” and that Russia had softened its stand by no longer airing its demands that Ukraine surrender.