French President Emmanuel Macron said on Friday he did not rule out sending fighter jets to Ukraine at some point, but that Kyiv was in need of more immediate military firepower, as Ukrainian officials said a fresh Russian offensive was under way.

Ukrainian President Volodymyr Zelenskyy has long urged Ukraine's allies to send jet fighters and on Thursday said that several European leaders were ready to supply aircraft.

"Europe will be with us until our victory. I've heard it from a number of European leaders ... about the readiness to give us the necessary weapons and support, including the aircraft," Zelenskyy told a news conference in Brussels, where he attended a European Union summit.