Kyrylenko said the strike came as "the workers had just finished their shift and were waiting at the bus stop for a bus to take them home from the factory."
"The Russians knew where they were aiming."
Avdiivka -- an industrial town north of separatist-controlled Donetsk -- is on the frontline of the war with Russia.
The coke plant -- one of Europe's largest -- has been the target of multiple attacks in recent years as Russia-backed separatist forces battled Ukrainian troops.
Russia has in recent weeks increased attacks on territories held by Kyiv in the eastern Donbas region, now the focus of its invasion of Ukraine.
Coke is a fuel with a high carbon content and is an important industrial product, used mainly in iron ore smelting, but can also be used as a fuel in stoves and forges.