As many as 600 kilograms of heroin worth around $50 million have been seized by law enforcement agencies in the Kyiv region, Ukrainian National Police head Serhiy Knyazev wrote on his Facebook page.

"I have never seen such a large quantity of heroin as the haul seized by the Ukrainian police. We are growing up. One hundred kilograms of this poison were seized overnight and another 500 kilograms were confiscated a few hours ago," he said.

The drug traffickers stored the heroin in Kyiv and then smuggled it to other countries, he said.

"Four people have been detained: a citizen of Moldova, a citizen of Turkey and two from Macedonia," Knyazev said.