Russia and Ukraine struck each other with hundreds of drones on Sunday, throwing Russian air travel in disarray, days after Moscow launched its largest aerial assault in the more than 3-year-old war.

Ukraine said it struck a Russian air base on Saturday, while Russia continued to attack Ukraine with hundreds of drones overnight as part of a stepped-up bombing campaign that has dashed hopes for a breakthrough in efforts to end the more than 3-year-old war.

Ukraine has concluded deals with European partners and a US defence company to step up the production of drones, President Volodymyr Zelensky said on Saturday. Zelensky said Kiev has "reached an agreement with one of the leading American companies to significantly increase our joint efforts" on drones,