Ukraine’s air force said on March 30 that Russian forces fired four missiles into eastern Ukraine overnight, as well as 12 Shahed drones across the country.

It said nine of the drones were shot down by Ukraine in the Dnipropetrovsk, Kherson, Odesa and Poltava regions. There were no immediate reports of casualties.

Russia has launched an air-strike campaign focusing on Ukraine’s energy sector over the past week, firing 190 rockets, 140 Shahed drones and 700 anti-aircraft missiles in what Ukrainian President Volodymyr Zelenskyy described as a “dramatic increase in Russia’s air terror.”

Russian forces are also “actively trying” to advance on the front lines, with 72 combat clashes taking place in the eastern Donetsk and Luhansk provinces over the past day, the Ukrainian military said in its daily bulletin.

Ukrainian forces repelled at least 40 Russian assaults near the cities of Avdiyivka, Bakhmut and Lyman in the Donetsk region and Bilohorivka in the Luhansk region, according to the bulletin.

“Ukrainian defenders pushed back 16 attacks in Lyman … and Bilohorivka, where the enemy — with the support of aviation — tried to break through the defenses of our troops,” the military said.

Ukraine has been forced onto a defensive footing on the front lines in the past few months as Kyiv struggles with ammunition shortages amid delays to a $60 billion aid package from the United States.

In an interview with The Washington Post published Friday, Zelenskyy warned that Ukrainian forces will have to retreat “step by step, in small steps,” if Kyiv doesn’t receive the U.S. military aid that has been blocked by political disputes in Congress.

“If there is no U.S. support, it means that we have no air defense, no Patriot missiles, no jammers for electronic warfare, no 155-milimeter artillery rounds,” Zelenskyy said, adding that his country is “trying to find some way not to retreat.”

Some information for this report came from Reuters and Agence France-Presse.