Ukrainian President Volodymyr Zelensky told AFP in an exclusive interview he expects Russia to step up its offensive in the northeast and warned Kyiv only has a quarter of the air defenses it needs to hold the front line.

Russian forces, which had made only moderate advances in recent months, launched an assault in the Kharkiv region on May 10 that has brought them their biggest territorial gains in a year-and-a-half.

Zelensky said Russian troops had managed to advance between five to 10 kilometers (three to six miles) along the northeastern border before being stopped by Ukrainian forces.

But he warned it may only be the “first wave” in a wider…