Ukraine and Russia attacked targets on each other's territory on Thursday after brief direct talks between the two sides failed to make any progress on steps to end nearly three-and-a-half years of war.

The warring sides remain far apart after the third round of U.S.-brokered peace negotiations on Wednesday. But there was progress on humanitarian issues.

Officials from Russia and Ukraine ended a third round of formal negotiations in Istanbul with an agreement to swap more prisoners but little sign of progress on a deal to halt the war.