Earlier this month, Trump set a 50-day deadline for Moscow to agree to a ceasefire, threatening fresh sanctions and tariffs if it failed to do so. Trump also announced new military support for Kyiv, with a particular focus on strengthening Ukraine's anti-drone and anti-missile defenses.

Deaths have been reported on either side of the border, just hours after a third round of ceasefire talks took place in Turkey.

Russia and Ukraine discussed further prisoner swaps on Wednesday at a brief session of peace talks in Istanbul, but the sides remained far apart on ceasefire terms and a possible meeting of their leaders.