Russian forces shelled Kharkiv, Ukraine's second-largest city, and devastated several towns in eastern Ukraine, while the European Union prepared sanctions on Russian oil sales after Germany said it was ready to back an embargo.

Russia launched a major offensive in eastern Ukraine focused on the Donetsk and Luhansk region after abandoning an assault on Kyiv at the end of March. Parts of those provinces were already held by Russian-backed separatists before President Vladimir Putin launched the invasion on Feb 24.

Ukraine's First Lady Olena Zelenska asked the West to maintain its support.

“Ukraine needs weapons so that...