Ukrainian President Volodymyr Zelenskyy is visiting Serbia as Russia launched another overnight wave of drone and missile attacks on Kyiv and the surrounding region, killing at least four people, including a three-year-old child, Ukrainian officials said Saturday.

Zelenskyy said three members of one family — a grandfather, grandmother and their three-year-old grandson — were killed by drone strikes in Pukhivka, in the Kyiv region.

Three other family members and a neighbor who attempted to help were hospitalized following the attack, authorities said.

Another person was killed in Kyiv after six ballistic missiles struck civilian infrastructure, according to Zelenskyy.

Ukraine's Air Force said it had shot down or intercepted 135 of the 151 drones launched by Russia overnight. The attacks caused damage across the Kyiv region as emergency services worked to assist those affected.

The latest strikes came as Zelenskyy traveled to Serbia, a country that has historically maintained close relations with Moscow. His visit highlights Ukraine's ongoing diplomatic efforts to strengthen relations with countries that have traditionally maintained ties with Russia.

Meanwhile, Ukraine's General Staff said Ukrainian forces carried out overnight attacks on Russia's Ilsky and Syzran oil refineries, with fires reported at both facilities.