Russia launched nearly 700 drones and dozens of ballistic and cruise missiles, primarily targeting civilians, in its biggest aerial barrage in almost two weeks, authorities said.

Moscow's forces have hit civilian areas almost daily since its all-out invasion of its neighbour more than four years ago, with the regular assaults occasionally punctuated by massive attacks. More than 15,000 Ukrainian civilians have died in the strikes, the United Nations says.

The latest bombardment came in the wake of Ukrainian President Volodymyr Zelenskyy's 48-hour trip this week to Germany, Norway and Italy in an urgent search for more air defence systems that can stop Russian missiles.

Ukraine has developed a significant domestic arms industry, especially in the production of drones and missiles, but it can't yet match the sophistication of U.S. Patriot air defence systems. Ukraine's top diplomatic priority is securing allies' help to buy and build more and better air defences, Zelenskyy said this week.

Cash-strapped Ukraine also needs the speedy disbursement of a promised loan from the European Union of 90 billion euros (USD 106 billion) that has been blocked by Hungary.