Ukraine said on Wednesday it had detained two Chinese nationals suspected of collecting data on its prized Neptune anti-ship missile, a key part of Kyiv’s growing domestic arms industry critical to its defense against Russia’s invasion.

Axar.az informs, citing Reuters, in a statement, the Security Service of Ukraine (SBU) said it had arrested a 24-year-old former student in Kyiv after the service passed him technical documents related to Neptune production.

It later detained his father, who the SBU alleged had aimed to pass the documents to Chinese special services. The agency added that he lived in China but visited Ukraine to “personally coordinate” his son’s work.

The Chinese Embassy in Kyiv did not immediately respond to a request for comment. A Ukrainian official told Reuters the two men were the first Chinese spies arrested since Moscow’s 2022 full-scale invasion.

Ukraine’s Neptune missile was used to destroy the flagship of Russia’s Black Sea Fleet in the first months of the war, and has since been fired at other targets including Russian oil terminals.

Kyiv has sanctioned Chinese companies for allegedly supplying Russia’s military effort in Ukraine. It also said it has captured Chinese nationals on the battlefield.

Beijing, a close ally of Moscow, says it has not armed any party in the war.